a.direct
b.inverse
c.joint
d.combined
![Adirectbinversecjointdcombined class=](https://ph-static.z-dn.net/files/d63/1bc6ad7db497d33375297b3fc94a3a27.jpg)
Answer:
c. joint variation
Step-by-step explanation:
Joint variation occurs when a variable varies directly or inversely with multiple variables. For instance, if x varies directly with both y and z, we have x = kyz.