Option 1 states that both the assertion and the reason are true and that the reason correctly explains the assertion. This is incorrect because the partition of Bengal did not end the role of the Moderates in the Indian freedom movement.

Option 2 contends both the assertion and the reason are true, but the reason doesn`t accurately explain the assertion. This is false because the assertion itself is not accurate.

Option 3 suggests that the assertion is true, but the reason is false. This is incorrect because the assertion isn`t true.

Option 4 is the correct answer. It posits that the assertion is false, while the reason is true. The reason is indeed true, as the Surat session of the Indian National Congress marked the formal split between the Moderates and the Extremists. However, the assertion is false because the Partition of Bengal did not mark the end of the Moderates` role in the Indian freedom movement. Instead, they continued to play a significant part.