To solve the inequality \( k + 1 < -3 \), we first isolate \( k \):
- Subtract 1 from both sides: \[ k < -3 - 1 \] \[ k < -4 \]
So the solution to the inequality is \( k < -4 \).
The correct option that expresses this solution is:
\[ { k : k < -4 } \]
Thus, the answer is:
\({k:k<−4}\)