What is visually different in the ecg reading from normal sinus rhythm?

The difference that can be found are:

Nodal rhythm: you can see the absence of the p wave (the first electric signal of an ECG)

Heart block: Heart block is a delay in the conduction of the electrical impulse through the atrioventricular node, the His bundle, or both branches, all located between the atria and the ventricles. There is a gap between the p and the rest of the ECG.

Atrial flutter: Designate atrial fibrillation whose amplitude, relative regularity and low frequency of the ripples are close to atrial flutter. Nevertheless, the f-waves are slightly irregular and rather positive in DII-III-VF shunts (unlike common atrial flutter). This aspect is in favor of a rather recent FA.

Atrial fibrillation: We observe:

*An absence of sinus wave P

*Auriculograms that vary anarchically in amplitude, shape, and frequency. They form a ripple of the baseline that may be relatively broad or barely visible (in aged forms), sometimes observed selectively in V1. These f waves can be confused with artifacts.

*Irregular RR intervals. 

Ventricular fibrillation: an Anarchic electrical activity of the ventricular myocardium. The resulting total desynchronization is responsible for circulatory arrest (asystole).

your answer is "the 1950's"

hey, i believe your answer would be d. sugar ribose and the base uracil. i believe this is the answer, because rna consists of sugar ribose, adenine, guanine, cytosine, and uracil.

your first option is incorrect, because that's dna. where it consists of sugar deoxyribose, adenine, guanine, cytosine and thymine.

your second option is also incorrect, this is because sugar deoxyribose is in dna, and uracil is in rna. these two do not make sense together.

your third option being incorrect, because sugar ribose is in rna, but not the base of thymine. rna consists of uracil, not thymine.

lastly your fourth option being correct! this answer is correct, because both sugar ribose, and the base uracil are in rna! ~

answer is d. sugar ribose and the base uracil.