Correct option is C. Both statements are correct.
An unambiguous grammar is not necessarily $\text{SLR}(1).$ But every $\text{SLR}(1)$ grammar is unambiguous.
We do have $\text{CYK}$ algorithm which takes $O(n^3)$ time (assuming size of the context-free grammar $|G|$ to be a constant) to parse any string of length $n$ using a context-free grammar $G.$