question_answer

Assertion : Survival of F. hepatica outside the hosts body is not so easy. Reason : Encysted body can survive outside the host body irrespective of the environment.

A) If both the assertion and the reason are true and the reason is a correct explanation of the assertion

B) If both the assertion and reason are true but the reason is not a correct explanation of the assertion 

C) If the assertion is true but the reason is false

D) If both the assertion and reason are false

E) If the assertion is false but reason is true

Correct Answer: C

Solution :

Due to complicated and prolonged life cycle, development stages have to encounter several hazards. First hazard is faced by encapsulated embryos as soon as they come out with faeces of primary host. They can not develop further if water (or moisture), suitable and temperature are not  available. Second hazard is encountered by miracidia which emerges from the capsules. If they are unable to make contact with a suitable soft part of the specific intermediate host within 24 hours, they perish. Cercariae which leave the intermediate host and swim into surrounding water are the next to face an uncertain future. If ingested by the vertebrate host, before they have encysted, they are destroyed by the action of hosts gastric juice. Finally, metacercariae are destroyed if they have to face a long period of dessication before they are ingested by a suitable vertebrate host.