The perineal injury can be prevented in normal labour by all except:
Now if you have ever been to labor ward and assisted or even seen a normal delivery, you know all the options given in the question are done to prevent perineal laceration.
The controversy lies in option b i.e. whether routine episiotomy should be performed: Well read for yourself what williams has to say on this issue.
“There once was considerable controversy concerning whether an episiotomy should be cut routinely. It is now clear that an episiotomy will increae the risk of a tear into the external anal sphincter or the rectum or both. Conversely, anteriortears involving the urethra and labia are more common in women in whom an episiotomy is not cut. Most, advocate individualization and do not routinely perform episiotomy.”
Hence option b is incorrect.
Steps done for prevention of perineal laceration : More attention should be paid not to the perineum but to the controlled delivery of the head.

Delivery by early extension is to be avoided. Flexion of the the sub-occiput comes under the symphysis pubis so that lesser suboccipitofrontal 10 cm (4”) diameter emerges out of the introitus.
Spontaneous forcible delivery of the head is to be avoided by assuring the patient not to bear down during contractions.
To deliver the head in between contractions.
To perform timely episiotomy (when indicated not routine).
To take care during delivery of the shoulders as the wider bisacromial diameter (12 cm) emerges out of the introitus.
Maintaining flexion of the head
Timely episiotomy as a routine
Slow delivery of the head in between contractions
Effective perineal guard