You might not be permitted to serve on a real jury.
Although there is nothing wrong with your reply that you are uncertain of whether you could impose a death sentence, the prosecutor in the case would likely argue that you would not be able to decide on the sentence by listening to both sides, but instead would be making your decision based on your doubts about the death penalty. The prosecutor would probably want you excluded from the jury by the judge. On the other hand, the defense attorney would probably argue that since you are not necessarily opposed to the death penalty in all cases, you could impose it in some cases, and you should be allowed to serve on the jury. Both the prosecutor and the defense attorney would probably ask you further questions to see how deep your reservations about the death penalty go.
To find out which answers would allow you to serve on a jury go back and choose each different answer.