B is the answer. my aunt has a malignant tumor and that means its active
A colorimetric method based on tetrazolium salts (e.g., MTT, XTT, CCK-8/WST-8) are especially useful for assaying the quantification of viable cells.
https://www.creative-bioarray.com/support/colorimetric-cell-viability-assay.htm
Answer: bidirectional regulator
Explanation: