Which line use can separate the main subject from the background?

Correct answer: Clear line on main subject and light line in background

Direct answer: A, use a clearer or heavier line on the main subject and a lighter line in the background. Line weight means the apparent strength or thickness of a line. If the important object receives stronger, clearer edges while distant or less important areas receive softer marks, the viewer’s attention is guided toward the subject. This creates visual hierarchy and helps separate foreground from background. B gives every area equal emphasis, so the subject may not stand out. C removes an important boundary and can make the subject difficult to read. D changes tone rather than demonstrating the requested line-use principle; it may sometimes help contrast, but it is not the best answer here. Memory cue: stronger marks attract attention; quieter marks recede.