改错：My elder sister has studies physics since eight months

my older sister has studied Physics since eight months.这句话错在 My older sister=My elder sister? my sweet elder sister 2 My sister has been working ()western China since graduated.A 求my sweet elder sister..谢咯 是My old sister 还是My elder sister My sister has many milk every day改错 My elder brother will be a PE teacher ____two months my sister has been staying in beijing for three months.这是什么时 my sister has been engaged for two months中为什么要用been? 一道英语的改错题My sister worked in that company since she graduated My sister studies hard .为什么不用hardly