The gel-like barrier between the serum and the clot in a coagulated blood sample is formed by a serum ________. 

In Western culture, 4 to 12 feet is considered public space whereas personal space is 1½ to 4 feet. _________________________

Indicate whether the statement is true or false

________ lasers can find pits in tooth enamel that may become cavities.

Fill in the blank(s) with the appropriate word(s).