I BELIVE 1. Is C. I’m assuming body mass just means the amount of bodies. So, the more bodies, the higher the population. You can have a high body mass, but still low density. For ex, if there are 30 ducks in a 10ft by 10 for pond, and 40 ducks in a 200ft by 100ft pond, the pond with 40 ducks technically has a higher population, but the density is much smaller because the ducks are spread out over a much larger space.
Number 7 is carrying capacity. When the graph levels out, that means the population has stopped growing because the environment can not sustain any more of the particular organism.