世界出口总额总是
A．小于世界进口总额
B．等于世界进口总额
C．大于世界进口总额
D．不是通常所指的国际贸易额
参考答案：A
The split between humans and living apes is thought by some scholars _____ 15 to 20 million years ago. [ ]
A. to occur
B. occurring
C. to have occurred
D. having occurred
