16.John enjoys      to listen       to pop music,      though       he is not      good at      singing      at all     . (A)to listen (B)though (C)good at  (D)at all

19.When you are looking to knock out a modest Firefox extension, there is no required to run out and buy the thickest reference book available at the bookstore nearby – since you can get whatever answer you need on the Internet. (A)no required(B)available (C)bookstore nearby(D)you need