Final answer:
The mechanical advantage of a block and tackle system with six pulleys is 6, assuming an ideal and frictionless system where the mechanical advantage is the number of ropes supporting the load.
Step-by-step explanation:
The mechanical advantage (MA) of a block and tackle system is determined by the number of segments of rope supporting the load. In a system where there are six pulleys involved, effectively, there could be six segments of rope that support the load. As a result, the mechanical advantage is directly related to the number of ropes supporting the load, which in this case would be six.
The question implies that the system is ideal and frictionless. Considering that, for an ideal system, the mechanical advantage is the number of ropes supporting the load, the answer is (a) 6. This means that the force applied is multiplied by a factor of six, allowing a user to lift heavier loads with less effort force applied.