Final answer:
Overhead secondary mains are typically installed on crossarms, which are bolted to the pole. High-voltage wires are supported by insulators but are not wrapped in insulating material. Isolation transformers usually have an equal number of primary and secondary turns.
Step-by-step explanation:
Overhead secondary mains are usually installed on crossarms and bolted to the pole. The correct answer to the student's question is a. Crossarms.
Regarding the true or false question, the high-voltage wires connected to tall metal-frame towers are indeed held aloft by insulating connectors, but these wires are not wrapped in an insulating material due to the high voltage and the requirement for efficient heat dissipation. Thus, the answer is b. false.
For the characteristics of a step-down transformer, the correct answers are that the primary voltage is higher than the secondary voltage, and usually, the primary current is lower than the secondary current because the transformer conserves power (and by extension, P=VI), so if the voltage is stepped down, in order for the power to remain constant, the current must increase.
Lastly, an isolation transformer typically has an equal number of primary and secondary turns, which is represented in answer c. It has an equal number of primary and secondary turns.