You need to use your head to solve this problem.

I often go birdwatching in the park on weekends.

He committed another crime while on probation.

Carbonate of soda is a versatile substance that can be used for laundry and cleaning.

His body showed a rejection reaction to the transplanted organ.

His single word triggered a chain reaction, and everything changed.

She overreacted to his words.

Nuclear reactions are used for mass production of energy.

I was surprised by his overreaction.

This rock is mainly composed of anorthite.