Where in the laboratory is long, unrestrained hair most likely to be a safety concern?
near an open flame
close to a fume hood
next to a concentrated sodium chloride solution
by a cabinet that contains flammable liquids

Option (a) is the correct answer.

Explanation:

Near an open flame the long, unrestrained hair is most likely to be a safety concern because hair catches fire very easily. Therefore, in the laboratories it is usually advised to tie your hairs properly in order to avoid any kind of accident.

There are also many chemicals that too can burn hairs but since they are kept in bottles therefore, they don't cause any harm as long as the bottle is in place.

Thus, we can conclude that near an open flame we should work more carefully.

yes the answer is total mass in unchanged   : )