To solve this question, the user needs to understand the correct form of the verb "realize" in the past perfect tense. The user should also be familiar with the meaning of the phrase "realize the figures" and how it relates to the context of the sentence.
Explanation of each option:
A. been realized: This option is incorrect. The past perfect tense of "realize" is "had realized," not "been realized." The verb "realize" is not a passive verb, so it does not take the auxiliary verb "been."
B. been realizing: This option is incorrect. The past perfect tense of "realize" is "had realized," not "been realizing." The verb "realize" is not a continuous verb, so it does not take the auxiliary verb "been."
C. realize: This option is incorrect. The phrase "had realized" is used in the past perfect tense to indicate that the realization occurred before another past event. The base form "realize" does not convey this meaning.
D. realized: This option is correct. The past perfect tense of "realize" is "had realized." In the context of the sentence, the past perfect tense is used to indicate that the realization occurred before the time of speaking or another past event. The correct form of the verb to use in this context is "realized."
The correct answer is: D. realized