贺卡: greeting card, congratulation card...
膝盖: knee, (Internet slang) to kneel down (in admiration)...
不起眼: unremarkable, nothing out of the ordinary...
芽: bud, sprout...
难免: hard to avoid, difficult to escape from, will inevitably...
过敏: oversensitive, allergic, allergy...
球员: sports club member, footballer, golfer etc...
繁忙: busy, bustling...
成效: effect, result...
保安: to ensure public security, to ensure safety (for workers engaged in production), public security, security guard...