Read this sentence from The Evolution of Useful Things.

Question

Making waterproof sandpaper would allow wet sanding, which in turn would cut down on dust, and thus be a great improvement.

The underlined phrases indicate

passing of time.
a directional change of position.
a cause-and-effect relationship.
sequence of events.

Answer 1

The underlined phrases indicate a cause-and-effect relationship. The sentence explains how making waterproof sandpaper (the cause) leads to wet sanding (the effect), which reduces dust (another effect) and results in a great improvement (a further consequence).