1. Fluroide helps protect a child's teeth while the teeth grow, but it is unharmful to their bodies.
2. Fluoride helps protect a child's teeth while the teeth grow, and it is not harmful to there bodies.
Which one is right.To me , The second one is right. But I found the first one right.Why as nothing contrast is here?
"but" suggests that something that protects teeth might nevertheless be harmful to the body. In certain contexts this may be intended (for example something else that is protective to teeth and yet harmful to the body has just been mentioned). In other contexts this suggestion would not be wanted, so "and" would be better.
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"but" suggests that something that protects teeth might nevertheless be harmful to the body. In certain contexts this may be intended (for example something else that is protective to teeth and yet harmful to the body has just been mentioned). In other contexts this suggestion would not be wanted, so "and" would be better.
"not harmful" is better than "unharmful".
(2) has a typo: "