**Choose the correct sentence:**
a) "If I will see her, I will tell her the news."
b) "If I see her, I will tell her the news."
c) "If I saw her, I will tell her the news."
What’s your answer?
Although (b) is better in most situations, (b) is also correct, and in some situations can actually be a better choice than (a). Let us give a name to the statement
S = "I will see her".
That statement is either true or false. (a) is equivalent to
"If S is a true statement, I will tell her the news".
In some situations, (a) is a better choice than (b). The primary function of "will" in English is to express certainty or willfulness. Although it can create future time reference, that is a secondary purpose is a corollary of its primary purpose. The meaning of (a) is very close to
"If I decide to see her, I will tell her the news."
It is a valid and useful sentence.