According to Piaget, the stage of cognitive development between 2 and 7 years of age, in which the child learns to use language as a means of exploring the world, is the ______ stage

Which of the following research topics on problem solving would have the lowest ecological validity?

a. How people plan their route through a hardware store, so that they can locate the items as quickly as possible. b. How diners in a restaurant figure out how to divide a bill fairly among themselves. c. How parents of preschoolers plan a birthday party. d. How students in a geometry class use information from previous problems to solve the current problem.

Compared to today where most Americans live until age 75, in 1900 the average life span was less than ___ years.

A) 55 B) 60 C) 50 D) 45