Teacher:In this task, you're given a question, a context passage, and four options which are terms from the passage. After reading a passage, you will get a brief understanding of the terms. Your job is to determine by searching and reading further information of which term you can answer the question. Indicate your choice as 'a', 'b', 'c', or 'd'. If you think more than one option is plausible, choose the more probable option to help you answer the question.
Teacher: Now, understand the problem? Solve this instance: Question: What other planes were fitted with the MG 15? Passage:As designed in 1931, the He 46 was a two-seat sesquiplane of mixed construction. The upper wing was swept back 10°. This is a common trick when a change in an aircraft's design moves the center of gravity to the rear; rather than moving the whole wing back to counter for the shift, it is easier to simply angle the wings back slightly, which requires very little change to the basic design, or even the overall structure of the wing. (The similarly angled wings on the Fairey Swordfish are due to just such a mid-program change to the weight distribution of the aircraft.) The tailplane was mounted high and braced by struts. The undercarriage was fixed, and the tail was fitted with a skid rather than a wheel. The He 46 prototype first flew in late 1931; its flight characteristics were good, but design improvements were incorporated. The small lower wing was removed, while the mainplane was increased in area by 22% and braced to the fuselage, transforming the He 46 into a parasol-wing monoplane. A more powerful engine was added to the second prototype, and a single 7.92 mm (.312 in) MG 15 machine gun for the rear seat was added to the third prototype.
 Links: a. MG 15 b. Prototype c. Monoplane d. Tailplane
Student:
a