Question

in which contraction does the apostrophe represent one missing letter

Who'd
They've
Don't
She'll

Answer 1

In the contraction "Who'd," the apostrophe represents one missing letter, specifically the letter "o" in "would."

- "Who'd" = "Who would" (or "Who had" depending on the context).

The other contractions you mentioned represent the omission of two letters:

- "They've" = "They have" (missing "ha")
- "Don't" = "Do not" (missing "no")
- "She'll" = "She will" (missing "wi")