Topic: Conjugation of Verb,

Best Answer Explained in Below-:

The past participle form of the verb "undertake" is "undertaken" (Option A). In English, the past participle is used primarily in perfect tenses and passive voice constructions. For instance, in the present perfect tense, we utilize it alongside an auxiliary verb: "I have undertaken a new project." Here, "undertaken" indicates that the action was completed at some point in the past.

To clarify the other options: "undertook" (Option B) is the simple past form of "undertake" and refers to actions completed in the past without auxiliary verbs, such as "I undertook the task yesterday." "Undertaking" (Option C) is the present participle form and is typically used to describe an ongoing action or as a gerund, for example, "Undertaking such a project requires careful planning." Finally, "undermine" (Option D) is a completely different verb that means to weaken or damage something gradually.

Understanding verb forms is crucial for proper grammatical structure. Hence, "undertaken" is the correct answer as it accurately represents the past participle form of "undertake."