The correct option is
B he was angered by the intrusion into his relationship with Lucy.
The correct answer is option B. After referring to the engagement party as appalling, Cecil specifically states that it is “disgusting, the way an engagement is regarded as public property” (line 19). He also explicitly states that “An engagement ... is a private matter, and should be treated as such” (line 26). Together, these comments indicate that he is angry because he feels the party intruded into his relationship by celebrating publicly something he strongly feels should be between only him and Lucy.
Although Cecil may have disliked the other guests, he does not comment on whether or not they were interesting, so option A is incorrect.
Cecil explicitly states in line 32 that he does not play tennis, so option C is incorrect.
Cecil only uses few Italian expressions in lines 33- 35, but throughout the passage he communicates in English without complaint, so option D is incorrect.