“四口”的安全防护应根据孔洞尺寸大小采取针对性措施。1.5m1.5m以下的孔洞，应预埋通长钢筋网或（）；1.5m1.5m以上的孔洞，四周必须设置防护栏杆，洞下张设水平安全网

A.加护坡

B.防护栏杆

C.加固定盖板

D.加支撑

Did you ever have someone’s name on the tip of your tongue and yet you were unable to recall it (1) this happens again, do no (2) to recall it. Do something (3) for a couple of minutes, (4) the name may come into your head. The name is there since you have met (5) person and his name. It (6) has to be dug out. The initial effort to recall (7) the mind for operation, but it is the subconscious (8) that go to work to dig up a (9) memory. Forcing yourself to recall (10) never helps because it doesn’t (11) your memory；it only tightens it. Students find the preparatory method help (12) examinations. They read over the questions (13) trying to answer any of them. (14) they answer first the ones (15) which they are most confident. Meanwhile, deeper mental activities in the subconscious mind are taking (16) ; work is being done on the (17) difficult questions. By the time the easier questions are answered, answers (18) the more difficult ones will usually begin to (19) into consciousness. It is often (20) a question of waiting for recall to come to the memory.

2（）

A.try

B.want

C.hesitate

D.wait