Which method bonds chips to substrates one at a time while heating and applying pressure, and is used to connect thin chips with large warpage and fine-pitch bumps?

Answer: C. Thermocompression bonding (TCB)

In thermocompression bonding, a bond head presses the chip while heating it, bonding the bumps one chip at a time. Unlike heating the whole assembly in a reflow oven, it can bond while holding down chip warpage, so it is used for stacking thin chips and connecting fine-pitch microbumps.