Change the following from active to passive: The university may confer honorary degrees upon exceptional scholars.

Correct — B. The active verb is may confer: a modal followed by the base verb.

A modal goes into the passive as modal + be + past participle, keeping the same modal:
may confer → may be conferred
honorary degrees (object) → subject
the university (subject) → by the university

Upon exceptional scholars stays as it is → option (b).

Why the others are wrong

• (a)
  Honorary degrees might have been conferred upon exceptional scholars by the university. — might have been conferred changes may to might and adds have been, the perfect. That moves the possibility into the past, which the active sentence never did.
• (c)
  Honorary degrees may have conferred upon exceptional scholars by the university. — may have conferred has no be or been, so it is not passive at all. It is the active perfect, and it makes the degrees the ones doing the conferring.
• (d)
  Honorary degrees must be being conferred upon exceptional scholars by the university. — must be being conferred swaps may for must, a different modal with a different meaning, and adds being, the continuous form. The active sentence has neither.

A voice change keeps the modal and the tense. Only the verb form changes: the base verb after the modal becomes be + past participle.

will announce → will be announced
must deliver → must be delivered
may confer → may be conferred

The object of the active becomes the subject, and the old subject becomes the agent after by. Everything else — here upon exceptional scholars — stays where it is.

Key facts

• Modal passive: modal + be + past participle, as in may be conferred or must be delivered.
• The modal itself does not change in a voice conversion: may stays may.
• Confer takes on or upon before the person honoured: confer a degree upon a scholar.

Common traps

• Picking may have conferred because it keeps may, without noticing that be is missing
• Accepting a changed modal, might or must, because the rest of the sentence matches

No directly related past PYQ was found.