The word "they' in line 8 refers to ______.
A. gasses
B. volcanoes
C. steam vents
D. rocks
查看答案
The passage suggests that oxygen remained in the atmosphere because ______.
A. it was caused by outgassing
B. it was heavier than hydrogen
C. hydrogen became trapped in limestone
D. rays from the sun created equal amounts of hydrogen and oxygen ______.
The phase “At any rate ”in line 26 is closest in meaning to ______.
A. regardless
B. in addition
C. although unlikely
D. fortunately
What is said about express mail？
A. It is very reliable.
B. It is quick.
C. It costs less.
D. It guarantees safe delivery.
What does the man suggest？
A. Paying in advance.
B. Placing an order.
Coming back after a week.
D. Choosing another pattern.
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