Normal heart sounds are caused by which of the following events? a) excitation of the sa nodeb) closure of the heart valvesc) friction of blood against the chamber wallsd) opening and closing of the heart valves

Which barrier to economic development is shown in the following examples? i. the high rate of hiv infection in underdeveloped nations ii. the use of children as soldiers in uganda’s army in the early 2000s iii. low literacy rates in underdeveloped nations with limited exposure to adequate education a. foreign debt b. political instability c. widespread disease d. low levels of social welfare

True or false a fertilized cell divides many times to form an embryo

Andrea's parents take her to a routine dentist exam. after examining andrea, the dentist applies a thin film on her healthy molars. what is this called?