Looking at the answers:

'Look for the traffic, and when you have seen it, acknowledge and turn right onto the new heading' --> INCORRECT. The first 2 words of the question indicate that you are under ATC instruction. In this situation, a call to act IMMEDIATELY would be followed. Looking for the actual conflicting traffic may not result in visual contact and in the meantime the separation is decreasing.

'Acknowledge the instruction then check visually that it is safe to turn before starting a turn right onto the new heading' --> INCORRECT. Aviate first, communicate later. To delay the turn while you respond on the radio would result in ever decreasing separation.

'Immediately select the maximum angle of bank possible and pull back to make the 60-degree turn as rapidly as possible' --> INCORRECT. ATC are controlling you based on an expectation of performance. A max angle bank would invalidate their attempt at separation.

‘Start a standard rate turn right onto the new heading immediately, and acknowledge the instruction when time permits’ → CORRECT. The instruction includes 'IMMEDIATELY'. ATC are controlling you based on expected performance of which includes a standard rate turn. Having entered the manoeuvre, then communicate with ATC.