(1)In_______Marx began to learn Russian.
A.a 1870
B.the 1870
C.the 1870's(没打错)
D.his 1870
(2)Please wait here.I'll be back in____hours.
A.two and half a
B.two and a half
C.half and two
D.two a half
(3)John began to learn Japanese by himself in__________.
A.the fifty
B.the fifties
C.his fifty
D.his fifties