What is the symbol for half-life?

The first one

Explanation:

Half-life (symbol t1⁄2) is the time required for a quantity to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable atoms survive.

i'm wiling to try and you : )

it's c (engineer's do their work with mechanical stuff not on any living being)