Convert litres to millilitres, then divide. Round up because partial bottles cannot be bought.<br><br>
&bull; 1.6 l = 1600 ml<br>
&bull; Bottles needed = 1600 ÷ 275 = 5.818...<br>
&bull; 5 bottles give 5 × 275 = 1375 ml (not enough)<br>
&bull; 6 bottles give 6 × 275 = 1650 ml (enough)<br>
&bull; Must buy 6 bottles<br>
<br>
Final Answer: C: 6