Based on the diagrams of the dolphin and the fish (not drawn to scale)...
Answer is option a)Only 2
Statement-1: They both have whiskers
Whiskers are hairs which portrude out from the nose of a mammal. Ex: Cat.
A dolphin has tiny whiskers but lose them later in life. But a fish is not a mammal so it is not common in both.
Statement-2: Each has a tail to propel itself forward in water.
Yes, this is true dolphins and fishes have tails to propel them forward.
Statement-3: Both have gills to breath.
A dolphin is a mammal and breaths through lungs like we do, that is why they come up to the surface of water to take in oxygen. Fishes have a special organ which helps them breath in water absorbong the dissolved oxygen from water. This organ is called gills, but it is not present in dophins. Therefore this statement is incorrect.
Statement-4: Both are warm blooded
A warm blooded animal is an animal which can keep up a constant body temperature independent of its surrounding temperature whereas cold blooded animals cannot keep a constant a body temperature and varies with the temperature of the surroundings.
Here, a dolphin is a warm blooded animal whereas a fish is a cold blooded mammal.
For your better understanding of warm and cold blooded mammals I will give you an example
-Humans are warm blooded animals. We can withstand extreme temperatures but still maintain constant body temperature
-Fishes are cold blooded animals. They cannot withstand changes in temperature. That is why you hear global climate disrupt the aquatic ecosystem as many cold blooded animals live in the ocean.