Here is a website that will help you find the answer and understand the poem as well...
http://www.sparknotes.com/poetry/hopkins/section4.rhtml
If you do not wish to visit the site I believe the answer is A.
Because she is mourning her own mortality, because man is mortal.
Answer:
A collective noun is a noun that represents a collection of individuals, usually people, such as: a team
for example: eleven football players a family
for example: mother, father and two children a crew
for example: 100 sailors
Explanation:
:)