In the article, Invasion of the Periodical Cicadas, why do scienctists believe that cicadas only reproduce every 13 or 17 years? Explain your answer with evidence from the text.

Hi, you've asked an incomplete question. However, I assumed you are referring to the article found on the Scientific American website.

Explanation:

Remember, according to that article we are told that scientists notice that these insects have a long nymphal (immature form before becoming adults) stage, one that can last up to 13 to 17 years on the ground before they leave the ground looking for mating partners.

Because it is only after mating occurs at this point that their eggs are laid, that is why scientists believe that cicadas only reproduce every 13 or 17 years.

the answer is b & c i believe : )

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.