用所给动词的正确形式填空
80. You had better get a doctor ______________ (pull out) your bad tooth.
81. It is the first time that he ____________(meet) the singer .
82. On the wall __________(hang) two beautiful pictures .
83. The school life he was used to _________(change) a lot since ten years ago .
84. The trees were cut down and that resulted in the city ___________(bury) by sand .
85. The old man urged that all the food ___________(buy) the next day .
86. The signs ______________ (indicate) the directions have been put up.
87. The experiment is being carried out, and it remains __________ (see) whether you are right or wrong about the results.