a)He came to Shanghai in the fall of 2008.他2008年秋天来到上海。b)He once worked in Shanghai．他曾在上海工作过。The above examples indicate that ______.

A．formal markers for tenses and aspects in Chinese are optional

B．formal markers for tenses and aspects in English are optional

C．formal markers for non-finite verbs in Chinese are obligatory

D．formal markers for non-finite verbs in English are obligatory