I guess most qs could be multiple choice, although I'd want some that weren't. For example:
1 Code the general format of the command to alter a table's column from char(30) to varchar(50).
2 Code the general format of the command to back up a database, specifying backup compression.
Those are really too simple to recognize in a multiple-choice format.
I suppose you could use:
A. ALTER TABLE table_name ALTER COLUMN column_name FROM char(30) TO varchar(50)
B. ALTER TABLE table_name ALTER COLUMN column_name varchar(50)
C. ALTER TABLE table_name ALTER COLUMN column_name varchar(50) NULL --or NOT NULL
One main idea there being if they don't issue ALTER commands, but instead change column types (solely?) thru the gui (yikes!), you'd want to be aware of that before you hired them, if you were still willing to hire them. To my mind, no "real DBA" would commonly, if ever, use the gui to alter a column's data type.
Naturally the qs would also vary considerably based on the level of DBA you're looking to hire.
I'll try to think of some more qs that would fit within the framework of "multiple guess".