1.My mum (make) you a sandwich if you (be) hungry. makes, are

will make, are

make, be

2.He (buy) a new computer tomorrow.

buys
will buy
am buying

3.You (not/understand) if you (not/listen).

will understand, doesn`t listen
won`t understand, don`t listen
don`t understand, won`t listen

4.
The scientists (invent) another fuel in the future.

invent
invents
will invent
​