A letter series follows a hidden pattern: a _ ba _ bb _ ab _ aab _ a. Which option correctly fills the five blanks in order?

Which single word correctly replaces the phrase 'jise taala na jaa sake' (that which cannot be postponed/avoided)?

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: Who comes back empty-handed?

Choose the word which is spelt correctly.

Respiration in aquatic animals takes place through which organ?