Question 14

all synthetic elements

a)are used in smoke detectors

b)are needed by the human body

c)are not typically found on earth

d)have more than 92 protons

All synthetic elements are not typically found on Earth.

Explanation:  

Synthetic elements are the man-made elements and for creating it additional protons are forced on the nucleus of an element where the atomic number should be less than 95 which is a very tedious process.

Synthetic materials are not naturally found on earth but are made by man in order to use for the better way of living. Synthetic elements are generally extracted from the plant and animal sources and used for betterment. The synthetic things are harmful for mankind and disrupts our nature. Synthetic fibres are of long chain of polymers which are made from single unit and bound together. The process for synthetic fibre is known to be polymerisation.

answer: 21

step-by-step explanation:

divide 630 by 30. 30 goes into 630 21 times

compost can be added to topsoil as a:

pesticide