No, the answer is false.
A salad would be an example of a mixture, as it is a blend of tomatoes and lettuce.
A salad would be considered a heterogeneous mixture (you can see its different components).
Yes, when the egg and a sperm cell meet fertilization has taken place
Viruses need to be inside a living thing (of course the living thing has to have the right temperature which most living things do) . When they're inside a living thing they start injecting the host's cells with its DNA in order to make more copies of itself which allows the virus to spread. So basically viruses need to be inside something living.
If all other resources are in adequate supply, then the light intensity will increase the rate of photosynthesis. To balance it out, other things then usually start becoming short in supply, so things often don't change.
B) sunlight
Sunlight supports life by providing food and warmth which is needed for the population of practically anything on earth to survive