Final answer:
The correct answer is D. The word 'waned' appropriately completes the sentences as it indicates a gradual decrease in the president's appeal or influence after a series of unfavorable decisions.
Step-by-step explanation:
The word that correctly completes both sentences is 'waned'. This is because 'waned' means to decrease in power or become weaker, which fits the context of both losing appeal and after a series of unfavorable decisions.
The president's appeal waned following many unfavorable decisions, suggesting that the influence or popularity of the president decreased after those decisions. Here, both 'dropped' and 'plunged' could theoretically work, but they suggest a more abrupt or precipitous decline, while 'waned' suggests a gradual decline, which is more appropriate over 'years of control'. 'Lightened' does not correctly fit here, as it generally refers to reducing weight or burden rather than decreasing in strength or popularity.