TASK DEFINITION: This task is about creating an unanswerable question based on a given passage. Construct a question that looks relevant to the given context but is unanswerable. Following are a few suggestions about how to create unanswerable questions:
(i) create questions which require satisfying a constraint that is not mentioned in the passage
(ii) create questions which require information beyond what is provided in the passage in order to answer
(iii) replace an existing entity, number, date mentioned in the passage with other entity, number, date and use it in the question
(iv) create a question which is answerable from the passage and then replace one or two words by their antonyms or insert/remove negation words to make it unanswerable.
PROBLEM: Passage: Bermuda's modern black population contains more than one demographic group. Although the number of residents born in Africa is very small, it has tripled between 2000 and 2010 (this group also includes non-blacks). The majority of blacks in Bermuda can be termed "Bermudian blacks", whose ancestry dates back centuries between the 17th century and the end of slavery in 1834, Bermuda's black population was self-sustaining, with its growth resulting largely from natural expansion. This contrasts to the enslaved blacks of the plantation colonies, who were subjected to conditions so harsh as to drop their birth rate below the death rate, and slaveholders in the United States and the West Indies found it necessary to continue importing more enslaved blacks from Africa until the end of slavery (the same had been true for the Native Americans that the Africans had replaced on the New World plantations). The indigenous populations of many West Indian islands, and much of the South-East of what is now the United States that had survived the 16th- and 17th-century epidemics of European-introduced diseases then became the victims of large-scale slave raiding, with much of the region completely depopulated. When the supply of indigenous slaves ran out, the slaveholders looked to Africa). The ancestry of Bermuda's black population is distinguished from that of the British West Indian black population in two ways: firstly, the higher degree of European and Native American admixture; secondly, the source of the African ancestry.

SOLUTION: What modern population contains one demographic group?

PROBLEM: Passage: Harvard's academic programs operate on a semester calendar beginning in early September and ending in mid-May. Undergraduates typically take four half-courses per term and must maintain a four-course rate average to be considered full-time. In many concentrations, students can elect to pursue a basic program or an honors-eligible program requiring a senior thesis and/or advanced course work. Students graduating in the top 4–5% of the class are awarded degrees summa cum laude, students in the next 15% of the class are awarded magna cum laude, and the next 30% of the class are awarded cum laude. Harvard has chapters of academic honor societies such as Phi Beta Kappa and various committees and departments also award several hundred named prizes annually. Harvard, along with other universities, has been accused of grade inflation, although there is evidence that the quality of the student body and its motivation have also increased. Harvard College reduced the number of students who receive Latin honors from 90% in 2004 to 60% in 2005. Moreover, the honors of "John Harvard Scholar" and "Harvard College Scholar" will now be given only to the top 5 percent and the next 5 percent of each class.

SOLUTION: What does a basic program also require?

PROBLEM: Passage: Glass is in widespread use largely due to the production of glass compositions that are transparent to visible light. In contrast, polycrystalline materials do not generally transmit visible light. The individual crystallites may be transparent, but their facets (grain boundaries) reflect or scatter light resulting in diffuse reflection. Glass does not contain the internal subdivisions associated with grain boundaries in polycrystals and hence does not scatter light in the same manner as a polycrystalline material. The surface of a glass is often smooth since during glass formation the molecules of the supercooled liquid are not forced to dispose in rigid crystal geometries and can follow surface tension, which imposes a microscopically smooth surface. These properties, which give glass its clearness, can be retained even if glass is partially light-absorbing—i.e., colored.

SOLUTION:
What does glass lack, allowing it to be polycrystalline?