The descriptions refer to conventional language and standard English, but one of them does not fit as well. Let's analyze each option:
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Follows grammar rules - This is a characteristic of conventional language and standard English.
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Uses simple vocabulary - This is not necessarily a characteristic of standard English, as standard English can include complex vocabulary as well.
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Has a serious tone - This can be a feature of formal or standard English, depending on the context.
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Has complex sentences - This is also a characteristic of standard English, particularly in formal contexts.
Based on this analysis, the answer is B (2), as using simple vocabulary is not a requirement of conventional language or standard English.