问题补充：
Some languages， Russian and German，are not easy to learn.
A. for example
B. such as
C. as
D. that is
答案：
A. for example
(答案→)B. such as
C. as
D. that is
解析：这句话是说,一些语言,如俄罗斯语,德语是不容易学习的. for example是举例说明， such as列举事例，as 做“象”讲的时候，是连词，that is也就是说，不符合句意，选B
