From what weight of a trailer and a semi-trailer is it obligatory to install an independent brake in them?

1. AIt is obligatory to install an independent brake in every semi-trailer and every trailer, regardless of their weight.
2. BIn a trailer and a semi-trailer whose permitted total weight is at least 19,000 kg.
3. CIn a trailer and a semi-trailer whose permitted total weight is at least 3,000 kg.
4. DIn a trailer and a semi-trailer whose permitted total weight is 8,000 kg and above.

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