Which level of organization is characterized by a group of cells that work together to perform a common function? organ
tissue
organ system
organism

tissue is characterized by a group of cells that work together to perform a common function.

ok yes, but what is the question? as soon as you ask the actual question i will answer it. : )

the circled areas are referred to   as sunspots.   the sunspots are cooler than the   surrounding area.

sunspots are temporary phenomena on the photosphere of the sun that appear visibly as dark spots compared to surrounding regions. they correspond to concentrations of magnetic field flux that inhibit convection and result in reduced surface temperature compared to the surrounding photosphere.