赞题库-背景图
单项选择题

The concentration of carbon dioxide is caused by_______.

A．the heat accumulated in the atmosphere
B．the burning of coal
C．the wide use of renewable energy
D．the destruction of the tropical rain forest
<上一题 目录 下一题>
热门试题

单项选择题A．toB．withC．onD．for

A．to
B．with
C．on
D．for

单项选择题The process by which carbon dioxide and oxygen are transferred does not depend on_______.

A．the presence of nitrogen in the blood
B．the muscles of the thoracic cavity
C．the flow of blood
D．the moisture in the air sac linings