Assertion: $Be{(OH)_2}$ dissolves in excess $NaOH$ solution.
Reason: $Be{(OH)_2}$ is an acidic compound.
A.Both assertion and reason re correct and reason is the correct explanation for assertion
B.Both assertion and reason are correct but reason is not the correct explanation for assertion
C.Assertion is correct but reason is incorrect
D.Assertion is incorrect but reason is correct

Hint: Acids are defined or known as those compounds which on dissolving and reacting in water give hydrogen ions. Bases are defined as those substances or compounds which when dissolved or reacted with water give out hydroxide ion. These are tested by litmus test and various indicators.

Complete answer:
Beryllium is a block element, present in the second period. The atomic number of berylliums is four, that means it has four electrons in the one atom of beryllium.
Now beryllium reacts readily with excess sodium hydroxide to form beryllium hydroxide which on further reaction with sodium hydroxide gives out $N{a_2}Be{(OH)_4}$. Let’s do the litmus test of the compound and it comes out to be basic which is red litmus blue.
Now if beryllium hydroxide is reacted with an acid. We will react with beryllium with an acid, hydrogen sulphate. In reaction the products we get are beryllium sulphate and water. Now the end product we get, let's do its litmus test and let’s see its nature. The blue litmus turns red, which indicates beryllium sulphate is acidic in nature.
Now beryllium hydroxide can be anything acid or base, depending on the reaction it is done with.
Assertion is correct but reason is incorrect.

Note:
Beryllium hydroxide on reaction with acid gives acid and on reaction with base gives a base compound. Such a compound which acts as both acid and base are called amphoteric compounds, compounds possessing both behaviours.