by the skin of (one’s) teeth

Do you know the English expression “by the skin of (one’s) teeth“? Read the conversation below. Can you guess the meaning?

Terry: How was your exam? Did you pass?

Kate: I passed by the skin of my teeth! The pass mark was 50 and I got 51!

Does it mean

a) have toothache when doing something

b) by a narrow margin

c) by one point

d) with difficulty

The answer is below! ↓

 

Answer: b) by a narrow margin