有关天体系统的叙述，正确的是：

A．最高一级的天体系统是星系

B．天体系统的层次是：地月系—太阳系—银河系—河外星系

C．太阳位于银河系的中心

D．形成天体系统的基本条件是相互吸引和相互绕转

. Inoculation(接种) of the H1N1 vaccine ___ launch another round to weak people in February,

but due to a global shortage, that has not happened yet.

A．was made to

B．was supposed to

C．was designed to

D．was hoped to