Combine the sentences using “and” or “but” (Viết lại câu sử dụng “and” hoặc “but”.) 1. Coal isn't very clean. It keeps us warm in the winter.

Combine the sentences using “and” or “but” (Viết lại câu sử dụng “and” hoặc “but”.)

1. Coal isn't very clean. It keeps us warm in the winter.