Which word is the comparative form of 'big'?

Is this sentence correct? 'An elephant is bigger than a mouse.'

What is the superlative form of 'fast'? Write one word only.

Choose the correct sentence.

Is the following sentence correct? 'This is the most bigger apple in the basket.'

Fill in the blank: Mary is the _____ student in the class. (Use the superlative form of 'smart')

Which word completes the sentence? 'Today is ______ than yesterday.'

Is this sentence correct? 'My dog is more friendly than your dog.'

What is the comparative form of 'small'? (One word)

Which is the superlative form?