Answer:
Metric ruler.
Explanation:
Metric ruler is a scale used to measure the heights of different objects. These metric rulers shows different measurement values and are easily available in the market.
Students have to measure the height of plants in the millimeters. The students should use the metric ruler as the measurement of the scale on millimeters. The metric ruler can be used directly to know the increase in the height of the plants.
Thus, the correct answer is option (C).
