Question

Which interrogative pronoun should replace the blank space in the following sentence?: ___ happened?

Answer 1

`color(red)("What")" happened?"`

Explanation:

Of the interrogative pronouns:
`color(white)("XXX")`Who
`color(white)("XXX")`What
`color(white)("XXX")`Why
`color(white)("XXX")`When
`color(white)("XXX")`Where
`color(white)("XXX")`Which
`color(white)("XXX")`How
only What can be used without any additional word before "happened"