Question: Out of the members of the Supremes who sang "A Breathtaking Guy," who remained in the group the longest?

Context paragraphs:
Mary Wilson (singer): Mary Wilson (born March 6, 1944) is an American vocalist, best known as a founding member and longest member of the Supremes.  Wilson remained with the group following the departures of other original members, Florence Ballard in 1967 and Diana Ross in 1970.  Following Wilson's own departure in 1977, the group disbanded.  Wilson has since released three solo albums, five singles and two best-selling autobiographies, "", a record setter for sales in its genre, and "Supreme Faith: Someday We'll Be Together"; both books later were released as an updated combination.

Where Did Our Love Go (album): Where Did Our Love Go is the second studio album by Motown singing group The Supremes, released in 1964.  The album includes several of the group's singles and B-sides from 1963 and 1964.  Included are the group's first Billboard Pop Singles number-one hits, "Where Did Our Love Go", "Baby Love", and "Come See About Me", as well as their first Top 40 hit, "When the Lovelight Starts Shining Through His Eyes", and the singles "A Breathtaking Guy" and "Run, Run, Run".

A Breathtaking Guy: "A Breathtaking Guy" is a 1963 song written and produced by Smokey Robinson and released first by Motown singing group The Supremes (1963) and later by The Marvelettes (1971).  The single was originally released under the title "A Breath Taking, First Sight Soul Shaking, One Night Love Making, Next Day Heartbreaking Guy" by The Supremes, but was shortened after its official release.  All three Supremes members - Diana Ross, Florence Ballard and Mary Wilson - sung the chorus with the original title together.

Please Mr. Postman (album): Please Mr. Postman is the 1961 studio debut album from Motown girl group The Marvelettes and the sixth album ever released by the company.  The focal track is the number-one hit single, "Please Mr. Postman".  The album notably features cover versions of label mates The Miracles' "Way Over There and "I Want a Guy", which was the debut single for fellow Motown girl group The Supremes the same year, and their cover had served as the b-side to "Twistin' Postman" the less successful follow-up to "Please Mr. Postman."  Although the original version by The Supremes flopped, The Marvelettes' cover became a regional hit.

Someday We'll Be Together: "Someday We'll Be Together" is a song written by Johnny Bristol, Jackey Beavers, and Harvey Fuqua and made popular as the last of twelve American number-one pop singles for Diana Ross & the Supremes on the Motown label.  Although it was released as the final Supremes song featuring Diana Ross, who left the group for a solo career in January 1970, it was recorded as Ross' first solo single and Supremes members Mary Wilson and Cindy Birdsong do not sing on the recording.  Both appear on the B-side, "He's My Sunny Boy."

Former Ladies of the Supremes: The Former Ladies of the Supremes, or FLOS (now "Scherrie and Lynda, Formerly of the Supremes"), is a singing group that was formed by former Supremes members Jean Terrell, Cindy Birdsong and Scherrie Payne, in 1986.  Though they weren't Supremes members, singers Sundray Tucker, Freddi Poole and Joyce Vincent have also sung with the group.

High Energy (The Supremes album): High Energy is the twenty-eighth studio album by The Supremes, released in 1976 on the Motown label.  The second album since 1968's "Reflections" (The Supremes Produced and Arranged by Jimmy Webb studio album released by The Supremes on the Motown label in 1972) include four Supremes members (not counting albums after Diana Ross was given individual billing containing outtakes from Florence Ballard's tenure in the group), it also is notable for featuring the last "Billboard" Hot 100 Top 40 pop hit for the group, "I'm Gonna Let My Heart Do the Walking".  The album sold around 125,000 copies in the USA.

Farewell (The Supremes album): Farewell is a 1970 live album by Diana Ross & the Supremes.  The album was recorded over the course of the group's final engagement together at the New Frontier Hotel and Casino in Las Vegas, Nevada, including the final night on January 14, 1970.  The show marked Diana Ross' penultimate performance with fellow Supremes members Mary Wilson and Cindy Birdsong.  At the conclusion of the show, new Supremes lead singer Jean Terrell was brought onstage and introduced to the audience.

Meet The Supremes: Meet the Supremes is the debut studio album by The Supremes, released in late 1962 on Motown.  The LP includes the group's earliest singles: "I Want a Guy", "Buttered Popcorn", "Your Heart Belongs to Me" and "Let Me Go the Right Way".  The earliest recordings on this album, done between fall 1960 and fall 1961, feature the Supremes as a quartet composed of teenagers Diane Ross, Mary Wilson, Florence Ballard, and Barbara Martin.  Martin left the group in early 1962 to start a family, and the other three girls continued as a trio.  Martin is not pictured on the album because of her departure earlier in the year; although her vocals are present on the majority of the recordings on the album (as well as other recordings made during that period), she never received any royalties from album sales.  She does have a spoken interlude line (as do the other group members) on the bridge of the song "(He's) Seventeen", and also sings lead on "After All", a song recorded for but not originally included on the album.  Along with these songs, Ballard and Wilson are heard out front on other songs as well.  Wilson sings lead on "The Tears" (another former non-album track) and "Baby Don't Go"; Ballard has leads on a handful of songs as well (see below), including "Buttered Popcorn" and the short intro line to "Let Me Go the Right Way".

Florence Ballard: Florence Glenda Chapman (née Ballard; June 30, 1943 – February 22, 1976) was an American singer.  Ballard was the founding member of the popular Motown vocal female group the Supremes.  Ballard sang on 16 top forty singles with the group, including ten number-one hits.  After being removed from the Supremes in 1967, Ballard tried an unsuccessful solo career with ABC Records before she was dropped from the label at the end of the decade.  Ballard struggled with alcoholism, depression, and poverty for three years.  She was making an attempt for a musical comeback when she died of a heart attack in February 1976 at the age of 32.  Ballard's death was considered by one critic as "one of rock's greatest tragedies".  Ballard was posthumously inducted to the Rock and Roll Hall of Fame as a member of the Supremes in 1988.

Supporting paragraphs: A Breathtaking Guy Mary Wilson (singer)
Answer: Mary Wilson