Answer: a. the amount of water
Independent variable can be defined as a variable which can be changed or manipulated in an experimental set up to record and observe it's effect on the dependent variable. A dependent variable is a variable which is dependent on the independent variable. The outcome of the dependent variable is the result of the experiment. A controlled variable is a variable which does not change in a reaction, and kept as a constant.
1. Here, in the given situation, the amount of water is an independent variable, as it can be manipulated or change in an experiment and it's impact on the growth of plant, which is a dependent variable needs to be observed.
2.Here, in the given, situation, the type of plant is a constant or control variable, as it is irrespective of the changes that occur in the dependent variable with respect to the independent variable.
The advantages of artificial blood are as follows -
a) It is easy to produce large amount of artificial blood and thus it helps in reducing the blood shortages.
b) The chances of spreading a disease through blood are also reduced as the blood is made in a safe and secure place. Also the full history of artificial blood is known to the doctors.