In 1H NMR spectra in which the solvent is acetonitrile-d3, labelled to an extent of 99.6%,...

In 1H NMR spectra in which the solvent is acetonitrile-d3, labelled to an extent of 99.6%, a multiplet is observed at δ 1.94 ppm. How does this multiplet arise, and what is its appearance? [D, I= 1; H, I = ]