Final answer:
Sentences (a) and (b) contain buried verbs. In sentence (a), 'make the assumption' can be simplified to 'assume', and in a sentence, (b), 'engaged in the preparation of' can be replaced with 'prepared'.
Step-by-step explanation:
A buried verb, also known as a nominalization, occurs when a verb is turned into a noun, often creating a more complex and less engaging sentence. Based on this, sentences (a) and (b) contain buried verbs.
In sentence (a), "make the assumption" can be replaced with "assume," and in sentence (b), "engaged in the preparation of" can be replaced with "prepared." Sentences (c) and (d) do not contain buried verbs because they do not include any nouns derived from verbs that can be simplified into a more direct verb form.