Who has responsibility to ensure the safety of food

The main responsibilities for all food businesses under the Act are:

to ensure you do not include anything in food, remove anything from food or treat food in any way which means it would be damaging to the health of people eating it
to ensure that the food you serve or sell is of the nature, substance or quality which consumers would expect
to ensure that the food is labelled, advertised and presented in a way that is not false or misleading
The guidance, which can be found at the link below, takes account of amendments to the Act in the General Food Regulations 2004 and the Food Safety Act 1990 (Amendment) Regulations 2004.

Aand b would both be correct