Questions

Error is in second part. Returning means coming back to place from where you began. So, the use of back after returned becomes redundant. Without using back, the meaning remains the same. We can omit ‘back’ in part b, and use ‘returned home.’

The two DNA strands are called polynucleotidesbecause they are composed of simpler monomer units called nucleotides. Eachnucleotideis composed of one of four nitrogen-containingnucleobases (cytosine, guanine, adenine or thymine), a sugar called deoxyribose, and a phosphate group.

The human ear can respond to minute pressure variations inthe air if they are in the audible frequency range, roughly 20 Hz -20 kHz. In fact, tests conducted show an increased sensitivity in the 3000 Hz range which is the optimal amplification frequency in the human ear. So, the sensitivity of the human ear varies with the frequency of the sound.

Nirbhay missile is India's first indigenously designed and developed long range sub-sonic cruise missile.It is designed and made by DRDO (Defence Research & Development Organisation).The Nirbhay missile can be deployed from multiple platforms.