D. All of the above
Quantitative data refers to data that you can measure or count. Typically it involves a number or measurement. B and C are both quantifiable as they are a number that you can count. You can count the number of petals on a rose or the number of rabbits and birds in an area. A is also quantitative because it is a measurement. If they remained at the same level, the measurement for the level of whatever substance has remained the same.