Soru

Biochemical engineers investigated the enzymatic degradation of polyethylene terephthalate (PET) microplastics using a newly isolated bacterial hydrolase.

Study 1
Four identical $250\text{ mL}$ reaction flasks were prepared, each containing $100\text{ mL}$ of a $50\text{ mg/L}$ PET microplastic suspension buffered at $\text{pH } 7.5$. To each flask, $0.10\text{ mg/mL}$ of hydrolase was added. The flasks were incubated for 24 hours at constant temperatures of $25^\circ\text{C}$, $35^\circ\text{C}$, $45^\circ\text{C}$, and $55^\circ\text{C}$, respectively, while continuously stirred at $200\text{ rpm}$. At the end of the 24-hour period, the mass loss of PET (in $\text{mg}$) in each flask was recorded.

Study 2
The procedure of Study 1 was repeated at a constant temperature of $45^\circ\text{C}$, but the enzyme concentration was varied across the four flasks ($0.05\text{ mg/mL}$, $0.10\text{ mg/mL}$, $0.15\text{ mg/mL}$, and $0.20\text{ mg/mL}$). PET mass loss was again measured after 24 hours.

In Study 1, which of the following correctly identifies the independent variable and the dependent variable?