Which RNA base bonded with cytosine?

Hey me with this one❤☺❤ how do you say that a cell also has a life span and death like an organism? give one example.

The concept of keystone species is controversial among ecologists because most organisms are highly interdependent. if each of the trophic levels is dependant on all others how can we say one is most important

What is true of sea slugs in these orders