海伦在星期四早晨有一节科学课,用英文怎么写这句话？

Helen has a science lesson on Thursday morning

海伦在星期四早晨有一节科学课,
Helen has a science class on Thursday morning,

Helen has a chemistry class on Thursday morning.

（如果她现在每个星期四早上都有的话）Helen has a science lesson every Thursday morning.
如果以前每个星期四都有的话就把has改成had然后在morning后加上 at the past
（即Helen had a science lesson every Thursday morning at the past.）
如果她以前有过单独一节在星期四的课就把has改成had再把every改成at
（即Helen had a science lesson at Thursday morning.）

回答和翻译如下:
There is a science class to helen on the thursday morning.
英语句子翻译。