What is the max effective rate of fire for the M4 rifle in semiautomatic mode?

The maximum effective rate of fire for the M4 rifle in semiautomatic mode is indeed 45 rounds per minute. This rate is determined based on the rifle's ability to deliver accurate fire while allowing the shooter time to recover between shots, maintain control, and ensure accuracy.

In semiautomatic mode, the shooter can fire one round per trigger pull, which requires a brief moment to aim and pull the trigger again. The M4 is designed for substantial accuracy at this rate, making 45 rounds per minute a balance between effective output and the need for precision in target engagement.

The other options represent significantly higher firing rates that exceed the practical and effective application of the M4 in semiautomatic mode, as they do not account for the time necessary to aim, control recoil, or achieve the desired effectiveness in engaging targets.