【正确答案】 A

【答案解析】Verb form; Idiom
This sentence asserts that a court decision has qualified a 1998 ruling. It then goes on to explain the series of conditions stipulated by that rulings workers cannot be laid off if they have been given (prior) reason to believe that continued satisfactory job performance will (always) ensure that their jobs are safe. To express these complicated temporal relationships, the present tense passive verb cannot be laid off describes the assurance provided by the ruling; the present-perfect, passive verb describes the prior condition have been given ... , and the future tense verb will be describes the outcome the workers can expect. The idiom reason to believe succinctly describes the assurance given to workers.
A Correct. The sequence of conditions makes sense, and the idiom is correct.
B The present tense are given fails to clarify that the assurance of job security must precede the workers' confidence that they cannot be laid off. The phrase reason for believing (singular, with no article) is unidiomatic and in this context is inappropriate.
C This version appears to be presenting having been given reason ... as a restrictive modifier of laid off. This makes the sentence very awkward and hard to make sense of and it obscures the requisite nature of the condition (that workers had been given prior reason to think their jobs were safe . Reason for believing is unidiomatic.
D Without a comma after off, it is unclear what having been given reason ... modifies; the string of infinitive phrases is awkward and confusing.
E As in (D), it is unclear what the participial phrase (in this case, given reason to believe) is supposed to modify.
The correct answer is A.