they were playing volleyball on the beach yesterday.为什么过去式用“playing”ing形式?

Were they all playing games?如何回答 They s___ they were playing football against Class Three. 英语翻译Biff and Chip were playing with wilfand wilma.They were playing in the sandpit.magic they were playing volleyball on the beach yesterday.为什么过去式用“playing”ing形式? They（ were playing football ）at that time.(对括号部分提问） ( ) were they ( ) at that time? yingyudanxuan When I came in,they games in the room..A.were playing B.are playing C.played D.plaWhen I came in,they games in the room..A.were playing B.are playing C.played D.plays They were playing football this time last saturday.too改成一般疑问句 they were playing computer games (at nine last night)对划线部分提问 when I got to the park,they were playing ( )there 这里填happy的什么形式 They were playing football ___it rained A.while B.when C.as D,before playing,were,they,childern,by,when,volleyball,passed,watching,their,I连词成句 We found some boys in the room.They were playing chess.(合并为一个句子） they became ____ in playing the piano and were talented in it They were playing chess happily.（改为感叹句）__ __ __ __ __ __! —How are the team playing?—They're playing well,—How are the team playing?—They're playing well,but one of them hurt.A.got B.gets C.are D.were they were (playingfoot) just now.对括号里的部分提问 （）（）they ()just nowthey were (playing football) just now. they are playing ball. 懂英语的请进,How long were they playing football yesterday?How long were they playing football yesterday?这里面的playing 是怎么用的?是什么词性,-ing不是现在进行时吗?为什么are已经变成were了,后面play还要用playing