How is the control group and experimental group different

The control group is the independent variable and the experimental group is the dependent due to change during the experiment. The experimental group will usually rely on another variable in the experiment for change.

Julia would be observing a. static electricity was caused by her sweater rubbing against her shirt and transferring electrons. she didn't touch anything metal, so that would cancel out b.she most likely didn't rub her sweater against her hair either, so that cancels out c.she also didn't scoot across the carpet while trying to take her sweater off, that cancels out d.so that leaves a.a. is correct.