A：2-甲基-1-丁烯
B：2-甲基-2-丁烯
C：3-甲基-1-丁炔
D：3，3-二甲基-1-丁炔
x∶120=3∶9
x=____
我国人口分布的地理界线是
—Excuse me! You can't take photos here．Look at the sign. It says “NO PHOTOS”．
— Sorry，I _________ see it and I _______ do it.
He school at 8 pm.
