Lavoisier made an important contribution to chemistry by
a)being the first to use the term "atom"
b)describing the orbits of electrons
c)discovering the proton
d) identifying substances by weight

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MY ANSWER IS "D". 
Great 
USING A RELIABLE BALANCE, LAVIOSIER REPORTED WEIGHT OF HIS REACTING SYSTEMs AND HE DEVINED THE "MASS CONSERVATION LAW". Chemists remembered him because by his several foreseing in actual Chemistry Dogma : 

-) Chemistry can't break down chemical elements ; 
-) Air is a mixture of Nitrogen and oxygen ; 
-) Oxygen allows combustion and animal breathing ; 
-) Oxygen combine with other chemical elements to form oxides or anhydrides ; 
-) Oxides unite water to form Bases ; 
-) Anhydrides unite to water to form Acids ; 
-) Acids unite to Base to form Salt besides rescued water ; 
-) Chemical Systems can't change its whole mass/weight.

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