Question

_____ three influenza type A virus subtypes(子類型) have been found in pigs.

A．By far

B．As far as

C．So far

D．Till far

Answer 1

C

C考查far短語辨析。句意：迄今為止，在豬身上共發(fā)現(xiàn)3種A型流感病毒的子類型。by far最----，-------得多，用在形容詞和副詞后；as/so far as 就---而言，遠到------；so far 迄今為止，主句常用現(xiàn)在完成時，分析have been found完成時被動語態(tài)可見so far符合句意和語言用法。