Calcium rich food will be most beneficial to prevent osteoporosis. For eg, milk, cheese, cereal, soybean, spinach etc.
Being underweight can contribute to a very frail and weakened immune system. It can make one feel tired mentally. And can also affect the bones by making them very brittle and frail sometimes.
A chronic illness and a communicable disease
The correct answer is D.
When designing a personal fitness program you should take into consideration what your goals are meaning what you want to realistically achieve, what activities you would like to do to get fitter and where and how you can do them and then create a variety of activities for yourself so you don't get bored and lose interest in your fitness plans.
This is a question that only you yourself can answer. No use of asking someone else to try and describe your aggression towards a family/friend.
