87. It is our duty to make c_____________ to protecting the environment.

86. PSAs are often placed for free and are intended to educate people about health, safety, or any other issue which affects public w__________.

85. After 32 years’ ________(缺席), China returned to the Olympic Games in 1984.

84.　Your v___________ is too small; you need to learn more words.

83. During the festivals, the ___________(商业的)centers are crowded with people.　

82. A lot of newly-planted young trees were d__________ in the typhoon.　

用所给中文提示或英文单词的适当形式完成下列句子，使句子完整正确。

81. I will ________(简要地)share some interesting facts and stories with you.