How does debt bondage compare/contrast to the forms of slavery in the past (chattel slavery)?

Dr. redbull conducts a study to determine whether her new energy drink children perform better on spelling tests. she randomly assigns children to one of two groups: group 1 receives her energy drink and group 2 receives water. she then gives both groups a spelling test and compares the results. which of the following is true about this study? a. group 1 is the dependent variable and group 2 is the independent variable. b. this is a correlational study. c. group 2 is the experimental group. d. the independent variable is the type of drink the children receive.

This cartoon appeared in 1916. the topic of the cartoon isa)the reason for the start of world war i.b)the success of us submarines in world war i.c)the military alliance between germany and mexico.d)the attitude in the us towards submarine warfare in world 

What does one prolonged blast and one short blast mean?