Which question can be used to form a hypothesis? A: How many different kinds of germs are on my hand?
B: Why is the sky blue?
C: Do cats or dogs sleep more?
D: All of the above.

relative humidity is a measure of the amount of moisture in the air relative to the total amount of moisture the air can hold.

so d

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.

im pretty sure its b

nacl or sodium chloride is an ionic compound. this is because an ionic compound pertains to a compound that consists of positively and negatively charged ions. in this case, na (sodium) has a tendency to lose one electron when it reacts with with other atoms, so the resulting sodium ion contains 11 protons and 10 electrons, thus making it positively charged (na+), when chlorine reacts, it usually gains one electron to form an ion called chloride, thus making it negatively charged ( since the ions are oppositely charged, they attract.