Demi solves 30 questions in 10 minutes. Which statement correctly describes the unit rate of questions per minute? O The unit rate is 1:3: Demi can solve 1 question every 3 minutes. O The unit rate is 3:1: Demi solves 3 questions every minute. The unit rate is 10:20: Demi can solve 10 questions every 20 minutes. O The unit rate is 20:10; Demi solves 20 questions every 10 minutes.