Task: Question Answering
Input (English): Problem: a test has 150 questions . each question has 5 options , but only 1 option is correct . if test - takers mark the correct option , they are awarded 1 point . however , if an answer is incorrectly marked , the test - taker loses 0.25 points . no points are awarded or deducted if a question is not attempted . a certain group of test - takers attempted different numbers of questions , but each test - taker still received the same net score of 40 . what is the maximum possible number of such test - takers ? 
Options: a ) 19 , b ) 21 , c ) 23 , d ) 25 , e ) 27
Output (English): c