A. create text file for writing, discard previous contents if any
B. create text file for update, discard previous contents if any
C. create text file for writing, do not discard previous contents if any
D. create text file for update, do not discard previous contents if any

Solution

B. create text file for update, discard previous contents if any

Explanation

w+ is a mode used to open a text file for update (i. e., writing and reading), discard previous contents if any.