The bomb was timed to e____ during the rush hour.

     Two men are walking in the park. One is Mr Brown , a worker, the other is Mr Black. Mr Brown is going to a chair. It is by the road. Mr Black is after him. Mr Brown finds Mr Black. Now Mr Black begins to walk faster(更快). Because he wants to get to the chair before Mr Black. Now Mr Black begins to walk faster because he also wants to get to the chair first. Then they both run .Mr Black runs faster than (比) Mr Brown. So he gets to the chair first and sits down on it. Mr Brown runs after Mr Black. When he gets to the chair. He sees Mr Black sitting on it. He is sorry to show a notice(通知)with the words“Wet Paint(油漆未干)”to Mr Black . Now Mr Black knows why Mr Brown is going to the chair.

下列关于豌豆植株的叙述，正确的是（　　）

90－30=（  ）

化学与人类生活密切相关，下列与化学有关的说法不正确的是（　　）