<p> 使用群集模块时，如何确定要启动的群集实例数量？( )</p>
<p> const numInstances = cluster.instances().length;</p>
<p> const numInstances = cluster.instances();</p>
<p> const numInstances = require('os').cpus().length;</p>
<p> const numInstances = process.cpus().length;</p>
