Question

Removal of phloem tissue leads to gradual death of the plant. Why does this happen?

Answer 1

Removal of phloem tissue leads to gradual death of the plant because  Distribution of carbohydrates from the leaves to the other parts of the plant is affected.
The plant will die because the phloem is like a veins for plants and it transport prepared food so without food the plant will soon die
so correct option is A 
hope it helps

Answer 2

Option A because phloem is concerned with transport of prepared food materials(carbohydrates) from leaves to other plant parts ,so if it get damaged the plant naturally dies