The correct answer is: Only 1.
A profit-maximizing monopolist will adjust his sales in the two markets so that his MR in each market just equals his MC. This is because the monopolist will want to produce at the point where marginal revenue equals marginal cost, which is the point of maximum profit.
Statement 2 is incorrect because a profit-maximizing monopolist will always adjust his sales in order to maximize profit. Statement 3 is incorrect because the monopolist will always adjust his sales so that MR equals MC, regardless of whether the markets are separate or not. Statement 4 is incorrect because the monopolist will always adjust his sales so that MR equals MC, regardless of whether MR is greater than or less than MC.