Question

definition
adds a value to a variable (e.g., counter += 1).
choose an answer
1 index
2 append
3 counter
4 +=

Explanation:

In programming, the += operator is used to add a value to a variable. For example, if counter is a variable, counter += 1 means take the current value of counter, add 1 to it, and then store the result back in counter. This is a common shorthand operation in many programming languages.

Answer:

1. +=