1)as time passes, which of these is decreasing?
a) amplitude
b) crest
c) trough
d) wavelength

2)which graph best represents the relative speeds of electromagnetic and mechanical waves through space?
a)
b)
c)
d)

3)which of these waves would have the greatest amount of energy?
a) a
b) b
c) their energy is equal
d) there is not enough information

pls me.

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.