The transgenic cow named Rosie produced milk enriched with human protein alpha lactalbumin at a concentration of  

The transgenic cow named Rosie produced milk enriched with human alpha-lactalbumin at a concentration of 2.4 grams per liter.

This nutritionally enhanced milk was designed to be more balanced than natural cow's milk, potentially benefiting infants and individuals with specific nutritional needs.

Therefore, the correct answer is: b) 2.4 g/litre