Question: Which statement is true about the sparse matrices?

1. You can use the `sparse` function to remove empty cells from cell array variables.
2. Sparse matrices always use less memory than their associated full matrices.
3. Mixtures of sparse and full matrices can be combined in all of MATLAB's built-in arithmetic operations.
4. The `sparse` function requires its input to be a full matrix with at least 50% zero elements.

Answer: The correct answer of the above question is Option B:Sparse matrices always use less memory than their associated full matrices.