Describing how the practical needs of a conductor shaped the creation of an instrument-(b) is overly general. the passage does not point to any specific newness in the sousaphones design, only difference compared to its predecessors, and further declines to state that the sound improved objectively, making (c) incorrect. (d) focuses on too small a portion of the passage, missing the overall idea at work. (e) does not fit, as the passage fails to make a claim about the superiority of one instrument to another, stating only that the sousaphone better suited sousas purposes than the helicon did. (a), which refers to the impetus for the sousaphones design and further describes how it was made to suit sousas particular needs, is correct.
