To find out how many centimeters the height of the plant increases in 2 weeks, we first need to determine how many days are in 2 weeks.
2 weeks = 2 × 7 days = 14 days.
Next, we know that the height of the plant increases at a rate of 3 centimeters every 2 days. To find out how many 2-day intervals are in 14 days, we divide 14 by 2:
14 days ÷ 2 days = 7 intervals.
Now, we can calculate the total height increase over these 7 intervals:
Height increase = 3 cm × 7 intervals = 21 cm.
Therefore, the height of the plant increases by 21 centimeters in 2 weeks.
The answer is C. 21 cm.