Mrs. Martin, a third-grade teacher, is instructing cursive writing. At first, she reinforces even crude attempts to reproduce letters with an encouraging word; as time goes on, though, she reinforces only well-formed letters. By reinforcing progressively better attempts at writing letters, Mrs. Martin is using:
Shaping

Shaping

Explanation: Shaping can be simply defined as the process of enforcing the development of a target behavior which an individual doesn't currently posses until that particular individual achieves or posses that target behavior.

The concept with which Mrs Martin is using to help the students reproduce letters and offering them encouraging words is call Shaping.

answer; for good luck