Which of the following assumptions underlying input-output analysis raises about its validity ?

I- The technical coefficients are fixed which means so substitution between inputs occurs
II- There are no externalities so that the total effect of carrying out several activities is the sum of the separate effects
III- Each good is produced by only one industry and each industry produces only one commodity
IV- There is no technical change
A. I and II only
B. I, II, III only
C. I, II, IV only
D. I, II, III and IV