Answer: Python Puzzler #861

The answer is B. The program prints:

***
***
***
***

Why?

The outer loop runs 4 times (one per row). Inside it, the inner loop adds 3 symbols to line. So you get 4 rows of 3.

Trace table

A trace table follows the program step by step. Here’s this one:

row	line printed
0	***
1	***
2	***
3	***

The code again

for row in range(4):
    line = ""
    for col in range(3):
        line = line + "*"
    print(line)