Which signal are you talking about?
Answer: B. Water breaks down into oxygen molecules for respiration.
Water is the required for photosynthesis, a process by which plants (terrestrial and aquatic) makes their food by utilizing water as a reactant to produce oxygen and glucose as product. The glucose act as a source of energy for conducting various metabolic processes in plants but oxygen is released in the air.

This oxygen is necessary for terrestrial and aquatic animals for respiration. Therefore, water breaks down into oxygen by the process of photosynthesis, hence water plays important role in respiration in living beings.
Climate change cannot be
measured with a single instruments but require thousands of measuring devices
that spread across the globe, land and under the sea. Thus,parameters
measured in climate change includes: Rainfall, Sunshine hours, Temperature, Relative
humidity, Atmospheric pressure, Wind speed .
However, there are various instruments used for the measuring of climate
change and they can be classified as follows: weather balloons and buoys, thermometers, wind anemometers,
Manual rain gauges, transmitting rainfall gauges and Automatic Weather
Stations
A chemical reaction happens