—______, thanks. I'd like a cup of tea.
A:Either
B:Both
C:Neither
D:None
— The box is too heavy to carry. What's in it?
— Jack _______ it with many books.
遗传病在人类疾病中非常普遍,对遗传病的发病率和遗传方式的调查是预防遗传病的首要工作。下面是对某种遗传病的发病率和遗传方式的调查过程,请回答下列问题:
点A在点O的南偏东30°,点B在点O的北偏西70°,则OA,OB这两条射线构成的角等于( )