"To je dobré mléko."

Translation: This is good milk.

[n03l14_l]

why "that is a good milk" is incorrect ?

[smailBerkK]

Because noun "milk" is uncountable in English, hence not using a/an here

[Anna426405]

'This milk is good' is also possible, a submitted for this as a correct answer. Thank you.

[BoneheadBass]

"This milk is good" is not an accepted translation because it is a different sentence grammatically. The course consistently distinguishes between predicative ("This IS good milk") and attributive ("This milk is GOOD") constructions of this type. You will run into this often as you move through the course, so it's good to understand it early on.

[Ivan496990]

Careful!
In croatian to je means he is^^

[AgnusOinas]

Nope, in Croatian it's just like in Czech - "to je" = "it is", and "on je" = "he is".

But of course, in both languages, you can point at a person and say "To je muž" (That's a man) instead of the (different) "On je muž" (He's man).