21．In recent years global warming is becoming concern for people all over the world.
A．the; the B．不填; a C．不填；不填 D．the; a
22.Last month, part of Southeast Asia was struck by floods, from ____ effects the people are still suffering．
A．that B．whose C．those D．which
23. In 1942, Columbus and his crew arrived ____ was so-called the New World by the westerners.
A what B in what C where D in which
