What is most important when selecting the right pfd for a passenger on board your boat?

Passenger's body weight and chest size

Explanation:

Finding a PFD (Personal Flotation Device) for a passenger requires you to find a PFD which fits the person properly for his/her required weight. There are three categories of sizes:

Men's size varies from small to 3x large where the chest size varies and the weight of the person is over 90 lbs or 41 kg

Ladies size varies from x small to x large where the chest size varies and the weight of the person is over 90 lbs or 41 kg

Kids weight varies from 90 lbs or 41 kg to 30 lbs or 14 kg

The PFD need to snugly fit to the person's body. So, to get the best fit you need to find the weight of the person and the corresponding chest size.

i don't understand. explain it clearly

when two balls of the different masses are dropped from equal height, they reach the ground at the same time .this is because they experience the same acceleration.

the acceleration is independent of mass.

thus when they are dropped they will always maintain the same velocity and travel the same distance (neglect air resistance of course) at the same time.