1000 SC- #18

yet is required to show contrasting actions

I feel that a continous tense is better in this case , as it describes a process of beating.......

here in option A , we shall analyze the three activities of the 'cells of the heart'
(1) adhere to one another (2) beating in unison and (3) adopting specialized orientations exclusive of one another.
'And' is used as a coordinating conjunction; expressing two elements to be taken together or in addition to each other. For connecting two noun phrase, adjective or adverb, or two clauses i a sentences. The use of 'and' here is to connect three 'peculiar features' of the heart cells makes option A valid. Thus option A is the correct answer.
In option B, Beat? No!. let's reference option A. The use of 'beating' as a present particle tense makes it suitable while option A uses 'beating' which properly signifies a continuous action of the heart cells. option B uses 'beat' which render it incorrect.
option C suffers same fate as option B. The usage of the verb 'beat' which is a present tense.
Option D also look accurate here but has some weak point which makes option A better and appropriate. 'Yet' being used here acts as an adverb and from what i know adverb to be, adverb are word that modifies a verb adjectives, other adverbs or various types of words, phrase or clauses. 'yet' does not modify anything here.
in option E, the use of the conjunction 'even though' makes this option sore to the eyes. It does not follow regular parallelism.