when you have been asked to prepare a meal that doesn't contain a certain ingredient, make sure that you don't cook it in oil that has already been used to cook other foods that could contaminate
pan fydd rhywun yn gofyn i chi baratoi pryd nad yw'n cynnwys cynhwysyn penodol, sicrhewch nad ydych yn ei goginio mewn olew a ddefnyddiwyd eisoes i goginio bwydydd eraill a allai ei halogi