Why does the narrator bites back her tongue ?

Answer: C. Time limits.

Explanation: When setting goals (in short, medium or long term) we need to follow certain steps to help us achieve them. The first thing we need to do is set specific definitions, this means to establish what specifically is what we want to achieve, if it can be measured somehow, then it is a good idea to set a number, in order to know objectively if we reach it, for example "my goal is to get at least an A- in the next math test." The second thing is realistic planning, this means to plan what we are going to do to achieve the goal, but it needs to be realistic, it is unrealistic to say "I'm going to study 12 hours a day everyday" because that is hardly going to happen, so instead of that we can say "I'm going to study 3 hours a day for the next two weeks." And the last element is establishing time limits, this helps us stay motivated and accountable, for example, "I need to be ready for the test, two days before."

Goals require specific definition, realistic planning, and time limits.

C. time limits

Hope this helps.