Observers in the Nineteenth Century Reported Seeing Many Straight-Line Features

Multiple Choice

Observers in the nineteenth century reported seeing many straight-line features crisscrossing the surface of Mars and interpreted them to be canals constructed by intelligent beings. What is the MOST likely present-day explanation for these observations?

A) The lines were rifts in the Martian surface at the boundaries of geological tectonic plates.
B) The lines were linear, stationary cloud formations (mountain lee wave clouds) and weather fronts moving around with the planet.
C) The lines were optical illusions caused by vague shadings on the planet's surface.
D) The lines were groups of dark volcanoes similar to those of the Hawaiian Islands on Earth.