Mandatory: required by law 强制的；法定的；义务的
It is mandatory for blood banks to test all donated blood for the virus.
血库必须检查所有捐献的血是否含有这种病毒。
The offence carries a mandatory life sentence.
这种罪行依照法律要判无期徒刑。

Clarify: to make sth clearer or easier to understand 使更清晰易懂；阐明；澄清
to clarify a situation/problem/issue
澄清情况／问题
I hope this clarifies my position.
我希望这能阐明我的立场。
She asked him to clarify what he meant.
她要他说清楚他是什么意思。

Supervise: to be in charge of sb/sth and make sure that everything is done correctly, safely, etc. 监督；管理；指导；主管
to supervise building work
监理建筑工程
She supervised the children playing near the pool.
她照料着在水池附近玩的几个孩子。