大量的生物遗体在适当的条件下沉积下来，形成铁、磷、煤、石油等有用矿产。
A. 对
B. 错
Which arethe common types of tests in teaching?
A. Placement test
B. proficiency test
C. achievement test
D. weekly or monthly test
What are the common ways that we can use to test children's speaking?
A. Sing a song
B. Oral interview
C. Talk about pictures
D. Role play
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