Question

if wire rope guardrails are used, what must also be done? select the best option. no further action is required they must be flagged with highly visible materials at least every six feet they must be flagged with highly visible materials at least every twelve feet

Explanation:

Wire rope guardrails are less visible than solid - type guardrails. To ensure safety and visibility, they must be flagged with highly visible materials at regular intervals. The standard is at least every six feet.

Answer:

They must be flagged with highly visible materials at least every six feet