Before the age of 23 weeks, the fetus cannot produce a liquid called ________ that lets the lungs transmit oxygen from the atmosphere to the blood

The Kim, et al. study (Oh Rats!)says that the greatest advantage of conducting a well-controlled experiment

vs. some other research design is (a) it allows for easier support of a hypothesis (b) it allows researchers to draw conclusions about cause and effect (c) it eliminates all researcher bias (d) it allows researchers to study behavior before it develops

International studies have shown that in several countries, smoking is more prevalent among

a. girls than boys. c. equally prevalent. b. boys than girls. d. neither boys nor girls.