In which type of arrhythmia do the atria contract very quickly and "out of sync" with the rest of the heart because of an error in the heart's electrical system?

A. atrial fibrillation
B. atrial flutter
C. ventricular tachycardia
D. Obradyarrhythmia

Organisms are classified, or grouped into categories, based on similarities in their characteristics and/or evolutionary relationships. the study of how organisms are classified is known as

Describe the response the kidneys have to dehydration and excessive water intake. what happens to the concentration of urine in each case ?

Sally and sue were investigating the topic of friction in science. they used a small car and a ramp as seen in the picture to test what they were learning. they knew that they slipped easily on waxed floors but not on carpet, so they decided to change the material on the surface of the ramp to see what happened. they planned to use glass, carpet, aluminum foil, and sandpaper and run the car down the ramp over each surface. what would be the best research question to guide the girls' experiment? a) does the amount of surface area affect the friction on the moving car? b) will the car travel fastest on the glass surface? c) how does the angle of the ramp affect the speed of the car? d)do rougher surfaces tend to create more friction than smooth surfaces?