Answer:
Option d and e are correct.
Explanation:
The expression for velocity of pulse in a stretched string can be given as follows
v =
where T is tension in the string , m is mass of string per unit length.
Use of lighter string of the same length, under the same tension amounts to higher m so velocity will decrease. Hence option d is correct.
Similarly, v is directly proportional to square root of tension. So if we increase tension , velocity also increases. So option e ) is correct.