Indicate whether each of the following descriptions better applies to phytochromes (P), cryptochromes (C), or phototropins (T). Your answer would be a four-letter string composed of letters P, C, and T only, e.g. TPCC.
( ) They respond to red light.
( ) They are found in animals as well as in plants.
( ) They are flavoproteins.
( ) They are dimeric, cytosolic serine/threonine protein kinases that are normally activated by autophosphorylation.