As shown here, which is not inflected for gender, number, or case; it refers to either persons or things; it is selective, that is, picks out one or more from a number of known persons or objects.
Use of what.
100. Sentences showing the use of interrogative what:—
Since I from Smaylho'me tower have been,
What did thy lady do?
—Scott.
What is so rare as a day in June?—Lowell.
What wouldst thou do, old man?—Shakespeare.
These show that what is not inflected for case; that it is always singular and neuter, referring to things, ideas, actions, etc., not to persons.
DECLENSION OF INTERROGATIVE PRONOUNS.
101. The following are all the interrogative forms:—
| SING. AND PLUR. | SING. AND PLUR. | SINGULAR | |
| Nom. | who? | which? | what? |
| Poss. | whose? | — | — |
| Obj. | whom? | which? | what? |