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