S1、S2是两个完全相同的波源，它们发出两列波长均为λ的简谐横波，图中虚线和实线分别代表某时刻这两列波的波谷和波峰．
（1）在空间有很多的加强点和减弱点，其中A、B、M、N、P、Q中是减弱点有______．
（2）根据图中的特征填写下表中的各项（下表中已给出部分物理量，请再根据给出的部分物理量的有关特征填写空缺项）
| 质 点 | P | Q | M | N | A |
| 到S1的距离 | 3λ | 3.5λ | 2λ | 2.5λ | |
| 到S2的距离 | 4λ | 2.5λ | 2λ | 1.5λ | 4.5λ |
（1）由图象知P、M为两列波的波谷和波谷相遇的点，A、Q、N为两列波的波峰和波峰相遇的点，这5个点到两波源的路程差为波长的整数倍，都是振动加强的点．只有B点是两列波的波峰与波谷相遇的点，到两波源的路程差为半个波长的奇数倍，则B点的振动减弱．
（2）A点振动加强，由图看出，A点到两个波源的距离相等，都是4.5λ．
| 质点 | P | Q | M | N | A |
| 到S1的距离 | 3λ | 3.5λ | 2λ | 2.5λ | 4.5λ |
| 到S2的距离 | 4λ | 2.5λ | 2λ | 1.5λ | 4.5λ |
| 完形填空。 | |||
| "See the doctor" In the waiting room,the patients (病人) , men and women,old and young,were sitting __1__ on the chairs, _2 _ for their turns. Billy, a school boy, was sitting there,too. They all looked very sad _ 3 _Billy. He _4_ an interesting story,and there was a smile on his face. Just then,the doctor came in to say he was ready for the next patient. Billy jumped up and ran into the __5 _ room. " Good morning, doctor!" " Good morning! What's your __6_ ,young man?"asked the doctor. _ 7_ Billy could say a word,the doctor made him _8_ down on a bed. "Now,let me listen to your heart. " Billy tried to speak,but the doctor told him __9_ anything."_10__,I'll take your temperature.”" Billy tried to sit up, but the doctor stopped him. "Now open your mouth... Mm, good."__11__with you.""I know there 12 _,"said the boy. "I just came to get some medicine for my father. " | |||
| ( )1. A. quickly ( )2. A. waiting ( )3. A. with ( )4. A. saw ( )5. A. patients ( )6. A. story ( )7. A. Before ( )8. A. to lie ( )9. A. say ( )10. A. After ( )11. A. wrong nothing ( )12. A. aren't | B. quietly B. waited B. and B. was seeing B. waiting B. trouble B. After B. lay B. not to say B. In B. something wrong B. are | C. luckily C. to wait C. except C. read C. sitting C. matter C. Until C. lying C. not say C. On C. nothing wrong C. isn't | D. noisily D. wait D. without D. was reading D. doctor's D. wrong D. While D. lie D. to say D. At D. wrong something D. is |