根据句意和汉语注释，写出单词的正确形式。

小题1:I’m sorry to say that those shoes in your size are not ____________ at our shop. (可以获得的)

小题2:He ______________ hard after he finished the 200-metre race. （呼吸）

小题3:The shirt with blood on it is one of the _________________.  (工程师)

小题4:Old people can’t get used to the new lifestyle _______________. (马上)

影响昆虫地理分布的原因有哪些？