Final answer:
Answering the student's question, True, carbon reacts with water vapor at elevated temperatures in a reaction that's important for producing synthesis gas. Additionally, increased sublimation does increase atmospheric water vapor, and higher trophic levels typically have less biomass due to energy loss.
Step-by-step explanation:
Carbon indeed reacts with water vapor at elevated temperatures in a process known as the gasification or water gas shift reaction, which is utilized in industrial processes. Hence, the correct answer is a) True.
At high temperatures, carbon (often in the form of coal) reacts with steam to form carbon monoxide and hydrogen, which is an important reaction for producing synthesis gas (syngas), a valuable chemical feedstock and fuel source.
When considering the water vapor content in the atmosphere, it's correct to say that increased sublimation would lead to more water vapor in the atmosphere. Also, regarding ecosystems, it is generally true that there is less biomass at higher trophic levels due to energy losses at each step of the food chain.
A reservoir for carbon can be the ocean, forests, or fossil fuels, which are considered reservoirs because they store large amounts of carbon for extended periods.