The correct options are
A Transportation of large boulders
C Carving large boulders using heavy tools
Each of the temples at Mahabalipuram were carved out of a huge, single piece of stone. Stone cutters had to work from top to down. It was difficult to find and transport big boulders. Sharper and heavier tools had to be used and was more laborious.
Whereas, brick structures like stupas are built up by adding layers of bricks from the bottom upwards. These structures were much easier to build as smaller materials were used. Simpler tools were used.