I think Jenny will become a good mother; she's very. __ with kids. a. existing ) b.open-ended C permanent d. gentle

The correct answer is d. gentle.

The sentence suggests that Jenny will become a good mother because she is very gentle with kids. Being gentle with children is an important quality for a good mother, as it indicates patience, kindness, and a caring attitude towards them. The other options, such as existing, open-ended, and permanent, do not accurately describe the quality needed for being a good mother.