question: A very rarefied medium will cause light to move
choices.text: faster slower
choices.label: A B
para: The more dense the medium, the slower the light moves.
para_anno.effect_prop: speed of light
para_anno.cause_dir_str: more
para_anno.effect_dir_str: slower
para_anno.cause_dir_sign: MORE
para_anno.effect_dir_sign: LESS
para_anno.cause_prop: density of a medium
question_anno.more_effect_dir: faster
question_anno.less_effect_dir: slower
question_anno.less_cause_prop: medium
question_anno.more_effect_prop: light
question_anno.less_effect_prop: light
question_anno.less_cause_dir: light