A or D. not sure 'bout it. sorry.
Answer:
b. [tex] {x}^{4} \:varies \: directly \: as \: y[/tex]
Step-by-step explanation:
[tex] \frac{ {x}^{4} }{y} = 7 \\ \\ \implies {x}^{4} = 7y \\ \\ \implies {x}^{4} \: \alpha \: y \\ {x}^{4} \:varies \: directly \: as \: y[/tex]
