Which of the following statements is correct? In the IR spectrum of 3-methyl-2-butanone, the most intense absorption is at 

(a) 3400 cm^-1 , owing to an OH stretching mode; 

(b) 1700 cm^-1 , owing to a CPO stretching mode; 

(c) 2000 cm^-1 , owing to a CH stretching mode; 

(d) 1500 cm^-1 , owing to the rocking of an isopropyl group.