Answer:Three challenges of life would be finding food and shelter and surviving .
Explanation:
When the sirens are heard, most likely people would go inside and turn on the local news to get more information.
The reactants in photosynthesis are:
6CO2
6H2O
Sunlight
B at the end of the study, since at the start would be problematic since that’ll make the participants behave differently, during the course will also make them behave differently for the remainder of the study, after publishing will create ethical issues and public problems. Answer is Option B.
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.