Now m____ do a lot of heavy work in factories,so people can have more free time.

Now m____ do a lot of heavy work in factories,so people can have more free time.
Now m____ do a lot of heavy work in factories,so people can have more free time.

Now m____ do a lot of heavy work in factories,so people can have more free time.
应该是：
machines机器
现在机器可以做很多重活,因此人们可以有很多的休息时间

machines 机器

machines 机器（复数）