Find the missing term in the letter series: A, G, L, P, S, ?

In the Rajasthani folk lullaby line 'Ila na deni aapni haaliyaan hularaay', what does the underlined word 'Ila' mean?

Read the following poem: 'Dubkiyaan Sindhu mein gotakhor lagaata hai. Jaa-jaakar khaali haath lautkar aata hai. Milte na sahaj hi moti gehre paani mein. Badhta doona utsaah isi hairaani mein. Muthi uski khaali har baar nahin hoti. Koshish karne waalon ki haar nahin hoti.' Question: What does the word 'Sindhu' mean?

Choose the word which is spelt correctly.

Respiration in aquatic animals takes place through which organ?