In the given figure, if AD, AE and BC are tangents to the circle at D,

In the given problem, the Right Hand Side of all the options is same, that is,

AB + BC + CA

So, we shall find out AB + BC + CA and check which of the options has the Left Hand Side value which we will arrive at.

By looking at the figure, we can write,

AB + BC + CA = AB + BF + FC + CD

We know that tangents drawn from an external point will be equal in length. Therefore,

BF = BE

FC= CD

Now we have,

AB + BC + CA = AB + BE + CD + CA

AB + BC + CD = (AB + BE) + (CD + CA)

By looking at the figure, we write the above equation as,

AB + BC + CD = AE + AD

Since tangents drawn from an external point will be equal,

AE = AD

Therefore,

AB + BC + CD = AD + AD

AB + BC + CD = 2AD

Therefore option (b) is the correct answer.