Here is the OE,
Nuclear testing on the planet is regulated by the Comprehensive Nuclear-Test-Ban-Treaty,
which was signed in 1996 by 71 states and prohibits all nuclear explosions, disallows scientific research, and is providing guidelines for proper handling of radioactive material to protect the environment.
(A) which was signed in 1996 by 71 states and prohibits all nuclear explosions, disallows scientific research, and is providing guidelines for proper handling of radioactive material to protect the environment.
The phrase “is providing guidelines ….” is not parallel in structure to “was signed in 1996 by 71 states,” “prohibits all nuclear explosions” and “supports scientific research.” All the list elements should have parallel structures.(B) which was signed in 1996 by 71 states and prohibits all nuclear explosions, disallows scientific research, and provides guidelines for proper handling of radioactive material to protect the environment.
CORRECT. The phrase “provides guidelines ….” is parallel in structure with “was signed in 1996 by 71 states,” “prohibits all nuclear explosions” and “supports scientific research.” All the list elements are parallel and the sentence does not contain any other verb/tense error.
(C) which, had being signed in 1996 by 71 states, prohibits all nuclear explosions, disallows scientific research, and guidelines for proper handling of radioactive material to protect the environment.
The verb construction “had being signed” is awkwardly constructed and grammatically incorrect.(D) which was signed in 1996 by 71 states prohibiting all nuclear explosions, and disallowing scientific research and the radioactive material’s proper handling guidelines to protect the environment.
Using the verb-ing form “prohibiting” just after the “states” incorrectly implies that the states are prohibiting “all nuclear explosions”; the treaty is the one which is doing the “prohibiting”. (E) having been signed in 1996 by 71 states and prohibits all nuclear explosions, disallows scientific research, and provides guidelines for proper handling of radioactive material to protect the environment.
First, the modifier introduced by the word “having” is grammatically incorrect; verb phrases must be preceded by a relative pronoun such as "which." Moreover, the modifier “having been signed in 1996 …” is not parallel with verb phrases “prohibits …, disallows …, and provides….”