In the common speech, the end vowel of the first alternative is only pluta,
This makes a niyama or restriction. The previous sutra, is thus confined to Vedic literature, and not to the vernacular. तु here has the force of 'only'. Thus अहि र्तू꣡ ३ रज्जुर्नु 'Is it a snake or a rope'? लोष्टो तू꣡ ३ कपोतोनु 'Is it a clod of earth or a pigeon ?'
The priority, of course, depends upon employment. The order of words depends upon one's choice.,