She is good at languages.language后要为什么要加s?

she is good at 【 】【swim】 she is good at------.she is a good------(skate) She is good at singing .She is good at dancing,too.She is good at _____ inging_____ dancing.同 She is good at Maths改为同义 She is good at English.(改成疑问句) Is she good at her school work? she is (good)than alice at swimming football at she playing good is She is good at math.（否定） she is good at ___(dance) 改错 she is good at sing She is not very good at _gardens She is good at maths because she is h_____. Ann has a good v___ .She is good at singing. she is good at French .she has a large v_____ she is good at drawing.She likes a___________very much. is she good at fishing同义句【】she【】【】in fishing She is good( at )swimming,介词为什么用at?