The weights of 4 boxes are 90, 30, 20 and 50 kilograms. Which of the following cannot be the total weight, in kilograms, of any combination of these boxes and in a combination a box can be used only once?
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'. The reason for (1)/ his failure is because (2)/ he didn't study at all. (3)/ No Error (4)