Electrocardiography (EKG) can be measured both noninvasively with electrocardiogram (and it's the most common, totally safe and painless method), as well as invasively with implantable loop recorder (used in extraordinary circumstances).
A first degree burn would be the immediate reaction
Answer: b. -CH_2OCH_3
Explanation: -CH_2OCH_3 has the highest priority according to the Cahn-Ingold-Prelog system used in assigning E and Z configurations of carbon-carbon double bonds