What is/are some methodological problems that confound results of the studies that use twin children to address the causal connection between parental education and their children's education? Select all.

A. On average, twin children obtain lower than their parents' educational level.
B. twin children are more likely to have the same environmental experiences, in addition to sharing 100 % DNA.
C. twin children tend to have difficult temperament which makes them difficult to study
D. twin children tend to differ from the general population of children in birth weight (i. e., lower than non-twin babies).

How is the city of savannah related to the union strategy of a full blockade of confederate ports? a) savannah was the last port needed to be secured in order to totally blockade the coast of georgia. b) savannah was the least significant city in georgia, and the union strategy centered on securing atlanta and capturing the tennessee river. c) savannah was the least significant city in georgia, and the union strategy centered on securing atlanta and capturing the chattahoochee river. d) savannah was the most significant port in georgia, and the union strategy centered on securing bases at savannah and the outlying islands to fully blockade georgia.