Article: In London Chopin took lodgings at Dover Street, where the firm of Broadwood provided him with a grand piano. At his first engagement, on 15 May at Stafford House, the audience included Queen Victoria and Prince Albert. The Prince, who was himself a talented musician, moved close to the keyboard to view Chopin's technique. Broadwood also arranged concerts for him; among those attending were Thackeray and the singer Jenny Lind. Chopin was also sought after for piano lessons, for which he charged the high fee of one guinea (1.05 in present British currency) per hour, and for private recitals for which the fee was 20 guineas. At a concert on 7 July he shared the platform with Viardot, who sang arrangements of some of his mazurkas to Spanish texts.

Question: What steet did Chopin stay on in London?
Ans: Dover Street

Article: When a tree is very young it is covered with limbs almost, if not entirely, to the ground, but as it grows older some or all of them will eventually die and are either broken off or fall off. Subsequent growth of wood may completely conceal the stubs which will however remain as knots. No matter how smooth and clear a log is on the outside, it is more or less knotty near the middle. Consequently, the sapwood of an old tree, and particularly of a forest-grown tree, will be freer from knots than the inner heartwood. Since in most uses of wood, knots are defects that weaken the timber and interfere with its ease of working and other properties, it follows that a given piece of sapwood, because of its position in the tree, may well be stronger than a piece of heartwood from the same tree.

Question: What hides the stubs of a tree's lost limbs from being visible later in its life?
Ans: Subsequent growth

Article: Burdened with debt, in 2004 Vivendi Universal sold 80% of Vivendi Universal Entertainment (including the studio and theme parks) to General Electric, parent of NBC. The resulting media super-conglomerate was renamed NBCUniversal, while Universal Studios Inc. remained the name of the production subsidiary. After that deal, GE owned 80% of NBC Universal; Vivendi held the remaining 20%, with an option to sell its share in 2006. GE purchased Vivendi's share in NBCU in 2011 and in turn sold 51% of the company to cable provider Comcast. Comcast merged the former GE subsidiary with its own cable-television programming assets, creating the current NBCUniversal. Following Federal Communications Commission (FCC) approval, the Comcast-GE deal was closed on Jan 29, 2011. In March 2013, Comcast bought the remaining 49% of NBCUniversal for $16.7 billion.

Question: In what month and year did Comcast buy 49% of NBCUniversal?
Ans: March 2013

Article: DC commutating electric motors, if fitted with laminated pole pieces, become universal motors because they can also operate on AC; reversing the current in both stator and rotor does not reverse the motor. But the now-standard AC distribution frequencies of 50 and 60 Hz caused difficulties with inductive reactance and eddy current losses. Many railways chose low AC frequencies to overcome these problems. They must be converted from utility power by motor-generators or static inverters at the feeding substations or generated at dedicated traction powerstations.

Question: How can low frequencies be obtained?
Ans:
converted from utility power