Files: AQA GCSE practice

Which file mode adds new data to the end of an existing text file without deleting what is already there?

1. "r"
2. "w"
3. "a"
4. "x"

What does this program print?

with open("scores.csv", "w") as f:
    f.write("Amy,72\nBen,58\nCal,91\n")

best = ""
top = 0
with open("scores.csv") as f:
    for line in f:
        parts = line.strip().split(",")
        if int(parts[1]) > top:
            top = int(parts[1])
            best = parts[0]
print(best, top)

AQA's pseudo-code guide has no file commands, so file handling is practised in Python. Which Python line opens `scores.txt` so that new lines are added to the end without deleting what is already there?

1. f = open("scores.txt", "w")
2. f = open("scores.txt", "r")
3. f = open("scores.txt")
4. f = open("scores.txt", "a")