Post parturient ketosis usually appears a. during lactation. b. when an embryo first becomes a fetus. c. during fertilization of an ova. d. during the first trimester of pregnancy.

The correct option is A.
Post parturient refers to the period after a living organism have given birth to offspring.  Post parturient ketosis is a type of ketosis that occur to a female animal after she has given birth to young ones. Glucose is the major fuel that living organisms used to generate energy, when there is shortage of glucose, the body use fat instead as fuel and this leads to the production and build up of ketone bodies. The build up of ketone bodies increases the level of ketones in the blood and this state of metabolismis called ketosis.