The correct option is B They secreted antithrombin in their milk after giving birth.
The correct answer would be option A. The passage clearly states that the antithrombin is active in the goat's mammary glands during milk production, i.e., it is secreted in their milk after giving birth. The statements of options B,C and D are in no way connected to the female goats mentioned in the passage. Thus, the other options are incorrect.