The right answer is option E in my view.Option A.
Probably as old as human society, and defined as the willful, malicious, and repeated following and harassing of another person", is stalking. Grammatically correct. We have a noun clause
Probably as old as human society, and defined as the willful, malicious, and repeated following and harassing of another person" serving as subject of the verb
is stalking. This is awkward at best, and inferior to option E. A simple noun subject such as
Stalking in option E, is better than a noun clause. Eliminate A.
B. Stalking
is probably as old as human society and
is defined as "the willful, malicious, and repeated following and harassing of another person". Grammatically correct, but there is no need to repeat
is after
and. It is awkward to make the modifier parallel to the main sentence, which is the definition of stalking. This option is inferior to option E. Eliminate option B.
C. Probably as old as human society,
the definition of stalking is "the willful, malicious, and repeated following and harassing of another person". This is wordy compared with option E.
staking is defined as is more concise. Eliminate option C.
D. "The willful, malicious, and repeated following and harassing of another person" is the definition of stalking,
which is probably as old as human society. A relative clause that conveys the same meaning as an adjectival phrase is considered wordy. Hence, this option is wordy compared with option E. Therefore eliminate option D.
E.
Probably as old as human society, stalking is defined as "the willful, malicious, and repeated following and harassing of another person". Correct. The most grammatically correct and concise option.