Final answer:
The correct synonym for 'enthralled' is 'excited', which corresponds to the feeling of being delighted or fascinated. Incorrect options such as 'upset' or 'horrified' do not capture the positive connotation of the word 'enthralled'.
Step-by-step explanation:
The synonym for the underlined word 'enthralled' in the sentence 'I was enthralled to learn I scored an "B-" on my test' is 'excited'.
The word 'enthralled' suggests a strong feeling of delight or fascination, which closely aligns with the feeling of being 'excited'. Therefore, option (b) excited is the correct synonym in this context. Neither 'upset' (a), 'horrified' (c), nor a combination of these feelings (d) correctly describe the sense of being enthralled.
It is important to understand the context in which words are used to identify their most appropriate synonyms. Words like 'disappointed', 'disturbed', or 'attended' do not match the positive emotion implied by 'enthralled'.