Circle/ highlight the letter of the characteristic used to classify a
mechanical wave.
a. the height of its crest
b. the depth of its trough
c. the way it travels through a medium
d. the type of medium through which it travels

no simpler subs form complex ones. synthesise = make

luster is not a good characteristic to use by itself because luster is the property of minerals that indicates how much the surface of a mineral reflects light. the luster of a mineral is affected by the brilliance of the light used to observe the mineral surface.

i think the answer would be reserve.

the skeletons of most mammals reach a certain size and then stop growing. however, many animals, including some mammals, keep growing throughout their lives. kangaroos, for example, just keep growing and growing until they die. also, the longer an animal lives the greater the chance it might catch some deadly disease.