缺少的是发现和创造，而不是市场。
远古人类会发现在缺少某种形式的机械辅助的情况下，这一过程是不可能实现的，这些辅助对他们来说不可或缺。
These aids would have been indispensable to very early people who would have found the process impossible without some form of mechanical aid.
我发现唯一缺少的是一个邮件模块可以访问电子邮件。
One thing that I find lacking is an email module to access your email.
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