Why doesn't a two battery flashlight work when one of the batteries is in upside down

Batteries work by having opposite sides “attract”, like magnets. When a battery is upside down, + and +, and - and - don’t work. They are like magnets. North and north sides can’t stick but north and south can. + and + cant stick, but - and - can.

The independent variable would be the fertilizer as it is what the dependent variable (the growth of grass) depends on.