N,N-Dimethylformamide (DMF) gives different patterns of signals for the methyl protons when its 1H NMR spectrum is recorded at different temperatures.Match the patterns of the NMR signals given in column I with temperatures given in the column II.                                            I                                                                        II(i) Two singlets,for three protons each, at δ 2.87 and 2.97 ppm   (x) 25 °C(ii) One sharp singlet for six protons at δ 2.92 ppm                        (y) 120 °C(iii) One broad signal for six protons                                                 (z) 150 °C