Parasitic wasps lay their eggs directly into the eggs of various host insects in exactly the right numbers for any suitable size of host egg. If they laid too many eggs in a host egg, the developing wasp larvae would compete with each other to the death for nutrients and space. If too few eggs were laid, portions of the host egg would decay, killing the wasp larvae. Which of the following conclusions can properly be drawn from the information above? (A) The size of the smallest host egg that a wasp could theoretically parasitize can be determined from the wasp’s egg-laying behavior. (B) Host insects lack any effective defenses against the form of predation practiced by parasitic wasps. (C) Parasitic wasps learn from experience how many eggs to lay into the eggs of different host species. (D) Failure to lay enough eggs would lead to the death of the developing wasp larvae more quickly than would laying too many eggs (E) Parasitic wasps use visual clues to calculate the size of a host egg. 答案是,A,OG解释也看了，不明白啊。人家的蛋的大小可以由它来决定？ The number of North American children who are obese-that is, who have more body fat than do 85 percent of North American children their age---is steadily increasing, according to four major studies conducted over the past 15 years.

If the finding reported above is correct, it can be properly concluded that

(A) when four majors studies all produce similar results, those studies must be accurate

(B) North American children have been progressively less physically active over the past 15 years

(C) the number of North American children who are not obese increased over the past 15 years

(D) over the past 15 years, the number of North American children who are underweight has declined

(E) the incidence of obesity in North American children tends to increase as the children grow older

答案是,C我怎么不明白呢？解释一下