题干
I _______ spend the Saturday afternoon with my old friends in the zoo, but they did not come.
A：was going
B：was to
C：will
D：was about to
答案(点此获取答案解析）
B
是γ射线放射源，可用于农作物诱变育种，我国用该方法培育出了许多农作物新品种，对