I said to him, 'Let us play'. Make it indirect sentence ?

The correct transformation of the direct speech "I said to him, 'Let us play'" into an indirect sentence is "I suggested him playing." Let's break down why this choice is appropriate.

In English, when we convert direct requests into indirect speech, we often change the structure and grammar to fit the new context. The phrase "Let us play" is essentially a proposal to engage in an activity together. In indirect speech, it is common to use verbs like "suggest" to convey proposals or recommendations.

Option C, "I suggested him playing," retains the essence of the original phrase. The verb "suggested" effectively captures the intent of the original sentence, which is to propose that they play together. The gerund form "playing" works here because after "suggest," it is grammatically correct to use the gerund to indicate ongoing action.

Other options are incorrect due to various grammatical issues:
- Option A uses "let us played," which is incorrect because "let us" should be followed by the base form "play," not "played."
- Options B and D, while closer to capturing the meaning, either miss the gerund use or lack clarity in who is involved in the action.

Thus, "I suggested him playing" is the most grammatically correct and contextually appropriate choice.