Abiotic because biotic is living. So abiotic is the opposite.
(A) Brighter, Because stars are 10 billion times brighter than the sun.
This is true , trees loose their leaves as a part of growth, also in seasons they loose leaves.
Yes, it is due to the presence of our diet. Meaning a persons digestive system can function non properly if using a different diet or if you have a poor diet, or a diet that does not fit to your body’s standard. So yes a persons digestive system is based on your diet.