Answer:
Excretion is the removal of material from one living thing, for example. Humans excrete tears, sweat, carbon dioxide etc.
Secretion is the movement of material from one point to another, for example. Humans secrete enzymes, hormones, saliva etc.
Basically in summary excretion is the removal of physical material and secretion is the movement of biological materials from one point to another.
I hope this was clear enough lol
1-no predators,so uncontrolled population growth
2-is a predator that is stronger than the apex predator of the area,or is in a predator free environment so has little to no problem spreading
3-is a toxic animal that breeds quickly,so when eaten can kill what ate it,there for ruining the ecosystem as the predators die from the toxic prey they eat.which can lead to method 1 if not dealt with.
I think this one is correct: C. You cannot view live specimens because the necessary preparation kills cells.