Photosynthesis is when plants use sunlight to synthesize food from carbon dioxide. Plants are autotrophs (they make their own food) and the food they synthesize creates carbohydrates, so the correct answer is D - autotrophs produce carbohydrates.
The horse will give 32 chromosomes and donkey will give 31 chromosomes to the offspring. The offspring has 63 in total. It is odd so it can not produce normal germ cell. So it is sterile.
