What I . . . . . . . . is that we . . . . . . . . to think seriously about a thorough reform in the legal system.

Solution (By Examveda Team)

In the given sentence "What I am proposing is that we begin to think seriously about a thorough reform in the legal system," the most suitable options to fill in the blanks are "am proposing" and "begin."

"What I am proposing" - The phrase "am proposing" is in the present continuous tense, indicating an action that is happening at the present moment. The speaker is expressing their current proposal or suggestion.

"that we begin to think seriously about a thorough reform in the legal system" - The verb "begin" is in the base form and refers to a future action that is expected to start soon. It suggests that the speaker wants the action of thinking seriously about reform to commence in the near future.

The other options do not use the correct verb forms for the given sentence. Option A, "have proposed/should have begun," uses the present perfect tense and the past perfect tense, which do not match the context of expressing a current proposal and a future action. Option B, "had proposed/were beginning," uses the past perfect tense and the past continuous tense, which are not appropriate for discussing present and future actions. Option D, "was proposing/have begun," uses the past continuous tense and the present perfect tense, which do not convey the correct sequence of events. Option E, "proposed/had begun," uses the simple past tense and the past perfect tense, which do not fit the context of current proposal and future action.

Therefore, the correct answer is "C. am proposing/begin."