The two all-round lights carried at or near the masthead of a pilot vessel on pilotage duty each show an unbroken light over an arc of the horizon of how many degrees?

Why A is correct

33 CFR §83.21(e) defines an all-round light as one showing an unbroken light over an arc of the horizon of 360 degrees. The two lights required by Rule 29 (§83.29(a)(i)) are all-round lights and therefore each cover 360 degrees.