Explanation:

- To ensure 'H < R' is true, S must be less than M. If S is less than or equal to M, and M is already less than or equal to R, H being equal to S maintains 'H < R'.

- To satisfy 'D = M', D should be greater than or equal to M.

- Now consider where the symbol is placed: between S and M.

- Option 1: ‘=’ makes S greater than or equal to M, which ensures D = M but doesn’t ensure H < R.

- Option 2: ‘=’ would make S less than or equal to M, and combined with M < P = R, it ensures both 'H < R' and 'D = M' because of its non-contradiction.

- Option 3: ‘<’ would make S strictly lesser than M; however, this doesn’t help establish 'D = M'.

- Option 4: ‘>’ would contradict the need for H < R.

- Option 5: ‘=’ could imply S equal to M, confusing 'H < R' since this creates potential equality, violating strict inequalities.

Correct Answer: Option 2: ‘=’