Answer:
The correct answer is:
<u>-ni</u>
No puedes permitir entrar ni vendedores <u>ni </u>perros callejeros.
Explanation:
necesitas;necesito
the first one should be <em><u>esta </u></em>
second one should be <u><em>estamos </em></u>
the third should be <u><em>es</em></u>
and the last one should be <u><em>son</em></u>