Answer:
B. Infinitive.
Explanation:
Infinitive exemplifies the basic form of verb without an articulation linking it to the particular subject or tense. They are also known as non-finite verbs. The italicized(bolded) words in the given statement illustrates infinitive clause as it justifies the above claim as in "to unpack" which is the basic form of verb binding the subject followed by adverb 'immediately'. Thus, the bolded phrase elaborates the infinite clause. The other options suggest an inappropriate claim as the C and D options must require 'ing' form of verb. However, the first option suggests verb but since it is used in the basic form, thus, it illustrates infinitive.
