At the beginning of a speech, it is very important to grab the audience's attention and make them interested in ______ you have to say.
A:which
B:what
C:that
D:who
①岩浆冷却较快 ②岩浆冷却较慢③在地表形成 ④在地下形成
下列卤代烃中沸点最低的是( )
《国家粮油仓储存管理办法》中明确规定:在常规储存条件下,粮油正常储存年限一般为小麦5年,稻谷和玉米3年.超过规定年限后,不能再作为粮食出售.原因是( )
如图所示,若AB∥DC,∠1=39°,∠C和∠D互余,则∠D=____,∠B=____.