Complete the sentence with a suitable option:

To say that we were surprised at the cleverness of the child is an understatement.
We were really _______.

The alternate judgment has a blank right after the adverb ‘ really ’. This means that the blank should immaculately be filled with an adjective, as adverbs describe a verb or an adjective. Now, the first judgment contains an adjective ‘ surprised ’. 
When we look at the meaning of the rulings, it states that the word ‘ surprised ’ was an understatement. So, we need to find a more violent interpretation of the adjective ‘ surprised ’, i.e. a reverse. The word ‘ surprised ’ refers to ‘ feeling or showing surprise ’. 
Now, we know the meaning, let’s look at the given options in the question above: 
a) irked- The word ‘ irked ’ refers to ‘ slightly angry; bothered'. This has a fully different meaning to the word ‘ surprised ’. It isn't the needed reverse. So, this is an incorrect option. 
b) astounded- The word ‘ astounded ’indicates to ‘ shock or greatly surprised ’. This has the exact same meaning for the given word. It's the needed reverse. So, this is the correct option for the following question. 
c) flattered- The word ‘ flattered ’ refers to ‘ lavish praise and respects on someone ’. This has an unconnected meaning to the given word. This isn't the needed reverse. So, this is an incorrect option. 
d) confused- The word ‘ confused ’ refers to ‘ unfit to suppose easily'. This has a veritably different meaning to the given word. It isn't the needed reverse. So, this is an incorrect option.