In the following question, some part of the sentence may have errors. Find out which part of the sentence has an error and select the appropriate option. If a sentence is free from error, select 'No Error'.
No one knows(A)/how he escaped(B)/being dashed to pieces.(C)/No error(D)
Among four students sitting in a row, average age of last three students is 20 years and the average age of first three students is 21 years. If the age of first student is 26 years, then what is the age (in years) of the last student?