A. False!!! Light weights are ok if you are doing a cardio/endurance type of workout with high repetitive movements such as Zumba. It will help burn a few more calories during aerobic activity. If you are looking to tone your body using weights such as dumbbells, barbells and weight machines, using light weight will not provide enough resistance to challenge the muscles and cause them to break down. Don't panic, the whole objective is to break down the muscle tissue. It's actually when you leave the gym and eat and rest that the body repairs the muscle tissue. The muscle tissue will be built up stronger and will help shape and tone your body. The misconception is, if you use heavy weight you will "bulk up". As long as you use weight heavy enough to perform higher reps - 8-12, you will not bulk up.
Unfortunately we can not "spot reduce" or lose body fat in specific desired areas. In most cases genetics will determine where we store and lose body fat (Thanks mom and dad!). But we can reshape our body by building and toning specific muscle groups with weight bearing exercises. More muscle = more calories burned at rest! In order to tone muscle, we have to provide enough resistance to challenge and break down the tissue. This in turn will cause the muscle to rebuild stronger and tone your body... True story!