Question

1. why does the brake pedal need to be pumped up after brake pad replacement?

○ to reset the master cylinder pistons
○ to fully seat the pads
○ to break in the pads
○ to set the correct brake fluid level

Explanation:

When brake pads are replaced, pumping the brake pedal helps push the caliper pistons out to fully seat the new brake pads against the rotor. Resetting master cylinder pistons isn't the main reason here, breaking in pads is a different process (done by normal braking over time), and pumping doesn't set brake fluid level (that's checked via reservoir). So the correct reason is to fully seat the pads.

Answer:

To fully seat the pads