We did'nt go hiking last weekend because of the heavy rain.=We did'nt go hiking last weekend because the rain was heavy.because +句子because of +名词或者名词短语问题后加三线，另一个后加五线~填空We didn‘t go hiking last weekend because 【it rained heavily 】.We didn’t go hiking last weekend because 【of the heavy rain】.也许是题目要求有误吧，五线没法填。