A group of students are setting up the first experiments, looking at the growth of roots in water containing an added factor. They have decided to grow seeds in both in pure tap-water and in water with a defined amount of vinegar added. As part of their group discussions they are keen to ensure that they all know what are the dependent variables that they are measuring in the experiment.

which two of the following would count as dependent variables in this experiment
1) How many seeds each student is using in the experiment.
2) The type of vinegar used.
3) The intensity of light that the seedlings experience.
4) The concentration of vinegar used.
5) The number of seeds which have germinated.
6) The length of the root

4 and 6 is correct help thanks

Not 4; it is an independent variable. I think it is 5 and 6, as the plant that benefits more (either from vinegar or tap water) will have more germinated seeds and the length of the root will increase.