根据句意和汉语注释，写出单词的正确形式。
____ The famous person often makes some ______________ (演讲)on protecting wild animals.
____ He feels happy by ________ (志愿) to work for the charity.
____ They have no money to afford________________(医学) treatment
____ They are very interested in these ________(发明).
____ He _________(表演) so wonderfully yesterday.
