Which statement best characterizes chemical reactions?
They always occur very quickly.
Their rates vary significantly.
Their rates are always slow.
They rarely occur in the natural environment.

Their rates vary significantly

Explanation:

Some reactions are highly exothermic for example, oxidation reaction, while some reactions are very slow for example, rusting of iron

"hydrogen bonding is the attraction of h atoms in the water molecule (slight + charge) to o atoms in a neighboring water molecule (slight - charge); it is a weak interatomic force. but it is still strong enough to the water molecules "stick" together."

because natural gas is colorless, odorless, and tasteless, distributors add mercaptan (a chemical that smells like sulfur) to give natural gas a distinct unpleasant odor (it smells like rotten eggs). they locate the types of rock that are likely to contain natural gas deposits.