用所给单词的正确形式填空，使句子意思完整。
小题1:It isn't easy _________(become) good English speakers.
小题2:On the __________(three) floor, there is a drugstore.
小题3:There are some ___________(different) in every country.
小题4:When we heard the funny story, we couldn't stop __________(laugh).
小题5:We should speak to our teacher __________(polite).
