Which structure surrounds the cell membrane of some cells, giving the cell a rigid shape

The pattern of this wave changes between its beginning and end. what is true about the amplitude and wavelength of the wave when the pattern changes?

The carbon cycle is best defined as a process in which a. carbon changes from inorganic forms to organic forms and back b. carbon is changed into other elements such as oxygen or nitrogen c. carbon is continually created from the sun’s energy by plants d. carbon is consumed and regenerated from other elements such as oxygen and nitrogen

Why do we perceive objects as retaining their brightness under different lighting levels?