Is my answer incomplete? Checking the stability of a system

Yesterday, during my exam, I had the following exercise:

Given $$H(s) = \frac{1}{s^2+2s+4}$$ check if it's stable.

which was supposed to be the hardest (since it was the last one). From my knowledge, I quickly found out the poles, checked the real part of the pole (which was $-1$) and said that the system is stable. Is my argument incomplete? Everyone in the classroom seemed to write a lot more at that final exercise.