There is/are two litres of milk in the jug.
Which form is preferable?
There is/are two litres of milk in the jug.
Which form is preferable?
I think when you refer to the quantity of milk or any thing alike you have to be so precise as follows:
Example:
a - In the city of Chicago there are many crimes every year.
b - In the city of Chicago there is much crime.
Here crime can be countable and can be uncountable according to the use in the sentences.
Let us take the most common habit between people as an example 'the coffee'.
How many coffees have you had to day? I have had three coffees.
How much coffee have you had to day ? I have had too much coffee today so I am going to stay awake very late tonight. Here I am talking about the quantity as a whole.
Because you are referring specifically to the two liters of milk, and there are two of them, even though they are 'in the jug,' one would use the plural 'are.'
If you were talking about milk in general, you might say, "There is milk in the two-liter jug." But since you are counting the liters, it calls for the plural form 'are.'
See Education First's explanation here.
Judging by the article, most of the confusion would be around seeking the plural of 'milk' itself (spoiler alert: there isn't one.)