Which statement correctly explains the aspect “Affirmed and negated sides of lā” in the example “زَيْدٌ قَائِمٌ لَا قَاعِدٌ”?

Qasr by Coordination, Negation–Exception, and Innamā

• Alternatives in coordination — Zayd is a poet, not a writer.
• Restrictive force of innamā — The believers are but brothers.
• Affirmed and negated sides of lā — Zayd is standing, not sitting.
• Word order after innamā — Zayd is only a writer.