[单选] A mean sun is used as the reference for solar time for three reasons. Which reason is NOT a cause for use of a mean sun?（）
A . The motion of the apparent sun is along the ecliptic B . Measurement of time is along the celestial equator C . The speed of the Earth's revolution is not constant D . There are variations in the Earth's rotational speed
简述组织液循环障碍的病理变化。
国际借记卡开户后系统自动开通（）活期主账户。 人民币。 美元现钞。 美元现汇。 港币现钞。 港币现汇。
The piston moving up and down keeps the crankshaft （）. to revolve。 revolved。 revolving。 to be revolved。
The piston moves up and down, thus causing the rotational movement of the（） crankshaft。 connecting rod。 cross-head。 main beating。
何谓岩石圈？地壳和岩石圈的区别是什么？
A mean sun is used as the reference for solar time for three reasons. Which reason is NOT a cause for use of a mean sun?（）
