![](https://cos-cdn.shuashuati.com/pipixue-wap/2020-1230-1107-56/ti_inject-812ce.png)
Nowadays, many drug companies are considering investing in the research and development of the anti-coronavirus vaccines (新冠病毒疫苗). (see for example https://baijiahao.baidu.com/s?id=1659196921040278665&wfr=spider&for=pc ) Do you think such R&D investments are strategic complement or substitute? Why? If a company succeeds in inventing an efficient vaccine, what do you infer about the best response of other companies? (Refine your answer in one or two paragraphs, Chinese is allowed)