Option 1: Air is being blown through the strands - This option is not relevant to the question as it is talking about air blowing through the strands while brushing, which is not the main reason for the strands moving away from each other.

Option 2: Static electric charges are being induced on the hair - This is the correct answer. When long dry hair is brushed, friction between the hair and the brush can cause a buildup of static electricity. This static electricity induces charges on the hair strands, causing them to repel each other and move away from each other.

Option 3: Mechanical energy is being transferred into heat energy - This option is not relevant to the question as it is referring to the transfer of energy from brushing into heat, which does not explain the movement of the hair strands.

Option 4: The gravitational attraction among the strands becomes smaller - This option is not relevant to the question as gravitational attraction does not play a significant role in the movement of hair strands during brushing.

In summary, the correct answer is option 2 because the buildup of static electric charges on the hair strands during brushing causes them to move away from each other.