Please answer this for me (8)

Which system revise and send electrical signals throughout the body

Are these strong bases, neutral, strong acids, weak acids or weak base household bleach (ph=12.6) fluid in a car's battery (ph of less than 1.0) milk (ph=6.7) stomach contents (ph=2.2) pure water (ph=7)

In general, characteristics that an organism survive and reproduce become more common over time. what mechanism of evolution causes this?