为什么我在单声道上收到此消息？ “警告FS0191：无法确定最高安装框架版本......”.NET“

I have installed Mono (version 2.4.2.1) on a Mac OS X (10.5.7) and i am trying to do some F# coding. The F# version i am using is 1.9.6.16.I have installed Mono (version 2.4.2.1) on a Ma