What are the implications of the two central metaphors — the spaceship and the lifeboat — that Garrett Hardin uses for his argument? Is contrasting these two an effective rhetorical strategy?

While I can't provide a direct answer I can provide aid.

Explanation:

The lifeboat in this metaphor is that in order for a lifeboat to keep itself sailing it needs teamwork, all of the people on the boat must work together in order to keep the boat afloat.

while,

The spaceship requires one commander. This commander keeps the spaceship in operation, their crew needs a leader in order to keep the spaceship intact.

simple terms: lifeboats require teamwork, spaceship requires a singular leader for guidance. Which is what they lack.

i think the correct answer would be adjustments in life roles.  this causes for one to adjust or change totally his/her career or lifestyle since the present is not beneficial to the life role he is at. for instance, you became a mother you would of course stop going to malls and enjoying life outside. you would be staying at home taking care of your child.