This is an intriguing question but one that is very hard to understand. I get the impression that you have a situation you don't know how to deal with. Possibly some young man has invited you to go for a walk with him and you don't know how to decline without hurting his feelings. The fact that you specify "in today's world" suggests that a girl might have been able to decline such an invitation in older times because her parents would not allow her to go out with young men unchaperoned--or something like that. It seems to me that--if I am right about my impression--your best bet would be simply to tell the truth as pleasantly as possible. Mark Twain once said, "When in doubt, tell the truth." I suspect that a truthful way to put it would be something like: "I'm sorry, but I'm not interested in starting a relationship with you." Maybe I have completely misinterpreted your question. But you shouldn't be going for walks with somebody if you don't feel like going for walks with that person, regardless of his feelings. Your own feelings are more important--and you could get into a more sticky situation by letter it escalate.