In a study of how vitamin e may reduce the risk of cardiovascular disease, one group was given a placebo, and the other group was given vitamin e supplements. the group that received the placebo was the group.

a. control

b. experimental

c. double-blind

d. hypothetical

Zoe decided to measure the hand length of each of her classmates. first she marked a line across each student's wrist and lined up a ruler from this mark to the top of the middle finger to measure the length. then she recorded the measurements in the table below. marla did this the same way for each classmate, and then zoe used this ruler to measure each straight line and record the data below. this data is invalid. what is the most likely reason why it is invalid? the ruler is marked in centimeters, but zoe recorded data in inches. the range of lengths is too wide, so zoe must have misread the ruler. marla’s complicated measuring procedure was overly confusing. marla could have been inconsistent while drawing outlines of fingers.

Awave has a wavelength of 15 mm and a frequency of 6 hertz. what is its speed?

In general, characteristics that an organism survive and reproduce become more common in a population over time. what mechanism of evolution cause this change?