In this task, you are given a sentence. You are expected to recognize the name of any form of chemical substances. Although there might be several correct answers, you need to write one of them.

[Q]: ARF represses androgen receptor transactivation in prostate cancer.
[A]: androgen


[Q]: Use of tranexamic acid for an effective blood conservation strategy after total knee arthroplasty.
[A]: tranexamic acid


[Q]: Exposure to valproic acid inhibits chondrogenesis and osteogenesis in mid-organogenesis mouse limbs.
[A]:
valproic acid