Final answer:
The price for 1 litre of the product at Shop1 is $1.80, which corresponds to option 1 in the given choices.
Step-by-step explanation:
The question from a student asks about the price of a litre of a product at Shop1, which is given as $1.80 per litre.
Among the provided options of 1) $1.80, 2) $2.00, 3) $2.20, 4) $2.40, the correct price for 1 litre at Shop1 is $1.80 per litre. Therefore, the answer to the student's question is option 1).