The sentence uses the inversion structure "Hardly had..."
which is typically followed by "when" to indicate that one event occurs immediately after another. Here, "Hardly had the train arrived when the passengers rushed to board" means the passengers rushed as soon as the train arrived. "Then" is used for sequential actions without inversion, "after" implies a delay, and "that" is grammatically incorrect in this context. Thus, the correct answer is: when
Complete the sentence:
``The proposal was accepted ___________ reluctance.''
Complete the sentence:
``Her ________ approach to solving problems impressed her colleagues.''
Complete the sentence:
``The team faced the challenge ___________ confidence, leading to their success.''
Rearrange the following parts to form a coherent and meaningful sentence. Choose the correct option.
P: and industries are exploring the use of biodegradable alternatives
Q: as plastic pollution continues to pose a significant threat to the environment,
R: governments, environmental groups,
S: to reduce dependence on single-use plastics