Critical Reasoning

Most homeowners' efforts to rid their gardens of dandelions depend almost exclusively on commercially available chemical herbicides. Such herbicides have a lethal effect only on the fully mature dandelion, but not on the seedlings of the plant, which at any given time outnumber the mature plants nearly twenty to one.

If one wished to rid one's garden completely of dandelions using only commercially available herbicides, one would most need to know the answer to which one of the following questions?

A)How long does the average fully mature dandelion live?
B)What is the length of the average life of a dandelion from seed to mature plant?
C)What percentage of dandelions in a garden are in the seedling stage?
D)Is there a period during which a dandelion is fully mature, but has not yet released its immature seeds?
E)How many seeds will the average mature dandelion produce?

I marked the answer as B but the OA is D
Can anyone please explain ?

Thanks,
Ankit

Answer D speaks about information that would greatly help get rid of dandelions using the commercially available herbicides.
What do we learn from the argument:
- the dandelion needs to be mature for the herbicides to work
- seedlings survive
Therefore, the homeowners need to attack dandelions when they are mature (otherwise the chemical won't work) and before they release seedlings (otherwise new dandelions will spread and grow very soon).

The length of a dandelion's life does not enter into it because the time itself has no influence over the facts mentioned above. What matters is the information asked about in point D.