1. That is not required. eliminate A,E
2. For appealing is unidiomatic. it should be "appeal to". Eliminate C
This leaves B and D
Here two events are involved 1. decision by the LC 2. Appeal to the HC
therefore perfect tense is required. Hence B wins.
This is already a good explanation. Let me add my two cents. '...plaintiffs in such cases fear that they will have no higher court that they can appeal to when their cases are decided in lower courts.'
1. Since the action started in the past [decisions made in lower court] and continues into the future [will not have a higher court to appeal to ], a present perfect form is required.
2. '...plaintiffs in such cases...'
Since the cases here is plural, the corresponding use should also be plural.
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