cold-blooded

他用冷酷无情的手段对待那些反对他的人。

He treated his opponents with ___cold-blooded cruelty.

那位冷血的老板毫不犹豫地解雇了几百名员工。

The ___cold-blooded boss fired hundreds of employees without hesitation.

蜥蜴是冷血动物，需要晒太阳来保持体温。

Lizards are ___cold-blooded animals that need sunlight to maintain their body temperature.