Which one of the following aspects is an exclusive characteristic

Which one of the following aspects is an exclusive characteristic of living things?

1. Isolated metabolic reactions occur in vitro
2. Increase in mass from inside only
3. Perception of events happening in the environment and their memory
4. Increase in mass by accumulation of material both on surface as well as internally.

All living things have an ability to respond to their environment, that is also called stimulation.