Ideally______for Broadway theatres and Firth Avenue, the AVw York Park hotel is n favounte with many guests.

A. locating                   B. being located            C. having been located  D. located

It has been proved______eating vegetables in childhood helps to protect you against serious illnesses in later life.

A. if                            B. because                   C. when                             D. that

Something as simple as______some cold water may clear your mind and relieve pressure.

A. to drink                   B. drinking                   C to be drinking       D. drunk

As his best friend. I can make accurate guesses about______he will do or think.

A. what                       B. which                      C. whom                     D. that

If there's a lot of work______. I'm happy to just keep on until it is finished.

A. to do                  B. to be doing             C. done                  D. doing

In recent years many football clubs______as business to make a profit.

A. have run               B. have been run         C had been run          D. will run

― Are you ready for Spain?

― Yes. 1 want the girls to experience that______they are young.

A. while                B. until                  C. if                     D. before

My sister, an inexperienced rider, was found sitting on the bicycle______to balance it.

A. having tried               B. trying                    C. to try                         D. tried

2．如图17所示，将质量M=1.20 kg的小沙箱，用轻质软绳（不可伸长）悬挂起来，开始处于静止状态，绳的长度l=0.80 m。用枪向沙箱发射质量m=0.05 kg的子弹，子弹以v₀=100 m/s 的速度向右水平击中小沙箱，并留在小砂箱中，小沙箱沿竖直面向上摆动。假设沙箱每次向左运动到最低点时就恰好有一颗同样速度的子弹射入沙箱，子弹射入沙箱的过程时间极短，可忽略不计，重力加速度g取10 m/s²，不计空气阻力。

   （1）求第一颗子弹射入沙箱的过程中子弹对砂箱的冲量大小；

   （2）求第一颗子弹射入沙箱并相对沙箱静止的瞬间，求砂箱对绳的拉力的大小；

   （3）求第一颗子弹射入沙箱后，砂箱摆动的最大高度；

   （4）要使沙箱摆动的最大角度小于60°，射入沙箱的子弹数目至少为多少

According to the air traffic rules, you______switch off your mobile phone before bearding.

A. may                        B. can                          C. would                     D. should