赞题库-背景图

单项选择题

According to the text, fossil studies of radiolaria are significant because they ______.

A．live in the depths of the ocean
B．are one-celled
C．have survived through the ages
D．demonstrate climatic changes prior to humans

<上一题目录下一题>

热门试题

单项选择题The best definition of biosphere as it is used in the text is ______.

A．the protective envelope formed by the atmosphere around the living earth
B．part of the earth and its atmosphere in which life can exist
C．the living things on earth whose existence is made possible by circulation of the atmosphere
D．the circulation of the atmosphere's contribution to life on earth

单项选择题According to the text, the fundamental cause of the ice ages is ______.

A．periodic changes in the earth's orbit around the sun
B．fossil remains of one-celled animals
C．alternating cold and warm seasons
D．changes in distance of the earth from the sun