Action of vitamin D3 is:
a) Increased calcium and phosphate absorption by 1,25-dihydroxyvitamin D3
b) Calcium and phosphate excretion may be decreased by 25-hydroxyvitamin D3 and 1,25-dihydroxyvitamin D3
c) Increased calcium and phosphate resorption by 1,25-dihydroxyvitamin D3; bone formation may be increased by 25,24- dihydroxyvitamin D3
d) All of the above