You are asked to heat a chemical solution in an open test tube. you should make sure that the test tube is pointed
a. away from nearby people.
b. towards a sink or a bucket.
c. so you can see the bubbles.
d. at a 180° angle from the flame.

Option (a) is the correct answer.

Explanation:

A chemical reaction is defined as the reaction in which there will be formation of one or more new product due to change in chemical composition of the reacting species.

For example,

A chemical reaction can be highly exothermic and rapid in nature. Hence, whenever we perform a chemical reaction then we must  keep the mouth of test tube away from nearby people as well as away from our own face.

This is because any kind of mishappening or accident can be avoided that may lead to serious consequences.

Thus, we can conclude that when you are asked to heat a chemical solution in an open test tube. you should make sure that the test tube is pointed away from nearby people.

law of conservation of matter

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%).