题干
Stephen Hawking has expressed his opinion ___ humans might one day be able to make spaceships capable of such speeds that time on board would slow down．
A：that
B：whom
C：which
D：what
答案(点此获取答案解析）
A
，
是两条不同的直线，
是一个平面，则下列命题正确的是 （ ）