Apiece of sodium metal when thrown in water catches fire. give reason

See below.

Explanation:

A lot of heat is produced in this reaction  so much that the sodium catches fire. If there is a lot of water and just a small piece of sodium it will not catch fire.  Potassium reacts more vigorously than sodium and will always catch fire.

answer: e.   sour taste

explanation: acids are those substances which dissociates in water to give ions. as they dissociate to give ions, they act as electrolytes and thus are electrically conductive. acids are sour in taste. example: hcl

bases are those substances which dissociates in water to give ions or accepts ions. as they dissociate to give ions, they act as electrolytes and thus are electrically conductive. bases are bitter in taste. bases are slippery in nature.

the answer is:  

line graphs show patterns in data with variables that change over time; whereas, circle graphs show data as parts out of a whole (such as out of 100%).