With 3 qestions for brainleist answer you

note: 3rd one has 2 parts
and 2nd part i need to know if im right

Why should seat belts not be mandatory quick plz

An object weigh 40n in air ,weigh 20n when submerged in water,and 30n when submerged in a liquid of unknown liquid density.what is the density of unknown of liquid?

This punnett square shows the cross between two pants. one parent has round seeds (rr). and the other parent has wrinkled seeds (rr) which best describes their offspring as shown in this cross?