Answer: A and D
Explanation:
D, because the defentition of quantitative means: measured by the quantity of something rather than the quality,
And A, because continuous means to continue the whole of something. In this case, you are continuing the research of the specific group of ducks.
Hmm I don't know in what way you're referring to, but something called yo-yo dieting<span> or the </span>yo-yo<span> effect might be what you're looking for. It's when someone looses weight and then regains it back.
Hoping I helped!</span>