Final answer:
Option A is a sentence fragment because it lacks a subject.
Step-by-step explanation:
In the given options, sentence fragments are incomplete sentences that lack a subject, a verb, or both. Let's analyze each option:
A. The engineer a new machine.
This is a sentence fragment because it lacks a subject. It should be corrected to "The engineer created a new machine."
B. The student studied all night, he was very tired in the morning.
This is a sentence fragment because it contains two independent clauses that are not properly joined. It should be corrected to "The student studied all night, and he was very tired in the morning."
C. Talking to the teacher in class often left the student confused. He had to visit his office hours.
This is not a sentence fragment. It consists of two complete sentences that are properly joined by a period.
D. He applied to many jobs all weekend, but only heard back from one company.
This is not a sentence fragment. It consists of two complete sentences that are properly joined by a comma and a coordinating conjunction.