Question

long hair in the laboratory must be
a cut short
b held away from the experiment with one hand
c tied back or kept out of the way with a hair band

Explanation:

In a laboratory, long hair poses safety risks. Cutting it short (A) is not necessary. Holding it with one hand (B) is impractical as both hands are often needed for experiments. Tying it back or using a hair - band (C) is the standard and safe practice to keep hair away from chemicals, flames, etc.

Answer:

C. Tied back or kept out of the way with a hair band