Which characteristic of life is demonstrated when single-celled organisms split in half, resulting in twice as many organisms as before? a) acquiring energy b) reproducing c) maintaining structure d) hardiness

The correct answer is option B, that is, reproducing.  

Reproduction refers to the biological procedure by which new organisms, that is, offspring get generate from their parents. Reproduction is a basic requirement of all the forms of life, every single organism prevails due to the outcome of reproduction. There are two modes of reproduction, that is, sexual and asexual.  

It is the phenomenon of asexual reproduction, in which a single cell species splits in half and results in the formation of twice as many organisms as before.  

Adverbial Clause :)

This is correct, and verified by many people.

D. Adverbial Clause