If you’re aerobically fit, you can
a. lift very heavy weights without injuries to your joints.
b. run a marathon without experiencing fatigue.
c. sustain a regular routine of exercise for 30-60 minutes with minimal fatigue.
d. quit your normal exercise routine without any negative effects.

I believe the answer is: C. sustain a regular routine of exercise for 30-60 minutes with minimal fatigue.

Our body is run through constant supply of oxygen. When we do aerobic exercise, the amount of oxygen supply needed to our body would be increased. So, when we keep pushing ourselves to the limit of our cardiovascular capability, our muscle would start to experience fatigue as a defense mechanism to reduce oxygen usage.

the plates spread at mid-ocean ridges (they are divergent plate boundaries) which allows magma to rise through the weakness between the plates. the magma then emerges as lava from the boundary and cools, creating a new crust.