The maximum number of existing transgenic animals is of:

'Rosie',a transgenic cow,is known to produce a type of milk which has all the following characteristics,except:

$A$: Transgenic mice are being used to test the safety of the polio vaccine.
$R$: It could replace the use of monkeys to test the safety of batches of the vaccine.

Read the following four statements $(A-D)$ and identify the mistakes in two of them.
$(A)$ The first transgenic cow,Rosie,produced milk which was human alpha-lactalbumin enriched.
$(B)$ Restriction enzymes are used in the isolation of $DNA$ from other macromolecules.
$(C)$ Downstream processing is one of the steps of $rDNA$ technology.
$(D)$ Disarmed pathogen vectors are also used in the transfer of $rDNA$ into the host.
Which of the two statements have mistakes?

After the safety of a vaccine is successfully tested in $.........$,it can be used in $.........$.

When and by which animal was the first human protein-enriched milk produced?