42（）

单项选择题What do we learn from the passage about solar wind activity （）

A. It affects the growth of trees.
B. It has been increasing since the Ice Age.
C. It is determined by the chemicals in the air.
D. It follows a certain cycle.

单项选择题The underlined word “penalty” is closest in meaning to（）.

A. punishment
B. trial
C. accusation
D. execution