Choose the number of correct statements related to factors affecting enzyme activity.

a)    Enzyme activity declines below and above optimum value of factor

b)    At low temperature, enzymes are temporarily inactive

c)    At high temperature enzymes are destroyed because proteins are denatured by heat

d)    Thermophillic organisms have enzymes which are stable at high temperature

e) With increase in substrate concentration the velocity of enzyme action rises  first and reaches a V_max