电镜下血小板内有许多细胞器，其中最为重要的是______、_________和________。
参考答案：α颗粒；致密颗粒；溶酶体
China's population is expected to increase to about 1.5 billion in 2040, ______it will start to decline slowly.
A．where
B．which
C．on which
D．after which
Table tennis is easy to learn, and, by the same token , boys don't need a lot of space to practice it.
A．by the same rule
B．symbolically
C．moreover
D．by logic
