Control Flow — if / else if / else

if-else chains

Use if, else if, and else to branch based on conditions.

Challenge: Write grade(score) that returns:

• 'A' for score ≥ 90
• 'B' for score ≥ 80
• 'C' for score ≥ 70
• 'D' for score ≥ 60
• 'F' otherwise