Answer:
Option B,They are not valid because the student did not control all the variables that can affect plant growth
Step-by-step explanation:
In case of water applied to the plants - the student watered the plant to which he has spoken by hand and to the remaining plants to which he has not spoken, he watered them by using sprinkler.
Water is an essential factor that effects plant growth. This factor must have been controlled. However, the water was given to both the plants only the quantity of water given varies in the two cases. Hence, the claim of student is not valid.
Hence, option B is correct
The numbers are 30 and 15. Length is 15 and width is 30.
Because it may be the only number that is common to both numbers. Like the greatest common factor between 2 and 3 is 1.
