Answer:
OPTION (A) : Testing a rock sample for gold content
Explanation:
For testing a rock sample of gold content you will need a Chemist. To test the material, the sample is rubbed on black stone which will leave a mark on the stone. This mark is tested by applying aqua fortis i.e nitric acid on the mark. If the mark gets dissolve then the material is not gold. If the mark sustain the it is further tested by applying aqua regia i.e nitric acid and hydrochloric acid which will prove the sample is of gold if it gets dissolve on using hydrochloric acid. The purity of the sample can be checked by differing the concentration of the aqua regia and comparing it with the gold material of the known purity.
The odysseyware answer is the same as his wood manure and food crops
Answer:
A.
Explanation:
the gradual movement of the continents across the earth's surface through geological time.
Answer:
An Element is a substance made up of only one type of atom as like gold, copper, oxygen, etc.
Copper sulphate with molecular formula 
, the elements are copper, sulphur and oxygen. It is formed by combination of 
cation and 
anion.
Copper sulphide with molecular formula 
, the elements are copper and sulphur. It is formed by combination of cation and 
anion.
The name of the covalent compound CCl4 is 'Carbon tetrachloride'.
Hope this helps!
