Answer 3

3.  Choice D is the correct answer.  With First Degree AV Block, there is just lengthening of the PR intervals.  There is no dropped QRS complexes.  Atrial Fib is irregularly irregular without P waves.  Second Degree Type I AV Block there is lengthening of the PR interval until the QRS complex drops. Third degree or complete heart block is when the P waves and QRS complexes are occurring independently of each other.  Each P wave does not necessarily have a QRS complex after it, and there is equal distance between the P waves and equal distance between the QRS complexes.