Question

1. the variable the was purposefully changed is number of oxygen bubbles lamp power the lenght of hte clippings the number of leaves the percentage of light

Explanation:

In an experiment, the independent variable is the one that is deliberately changed to observe its effect on another variable. Here, the experiment seems to be related to photosynthesis in aquatic plants, and the factor that is purposefully modified among the options is the lamp power which can affect the rate of photosynthesis and thus the number of oxygen bubbles produced.

Answer:

lamp power