A greenhouse is built with clear glass or plastic panels that allow sunlight through: trapping the heat inside. This is an example of a (n)
a) high temperature parabolic collector
b) active heating solar structure
c) passive heating solar structure
d) photovoltaic cell

thymine. in rna, thymine is replace by uracil

hormones in blood stream

image: dtc.ucsf.edu

endocrine glands secrete hormones into the blood stream near them; the hormones then travel in our bloodstream until it reaches its destination, called a target cell, in distance parts of the body. in the target tissue, hormones lock onto the target’s plasma membrane, called the receptor site.

i believe the answer is c

if the type of the food available changes, then the frequency of beak types will change, because birds with beaks more suited to the available food will be more successful over time.