a) A = \(\left(1-\frac{1}{2}\right)\). \(\left(1-\frac{1}{3}\right)\). \(\left(1-\frac{1}{4}\right)\). . . . . \(\left(1-\frac{1}{1000}\right)\)
b) B =\(\left(1-\frac{1}{5}\right)\) \(\left(1-\frac{2}{5}\right)\). \(\left(1-\frac{3}{5}\right)\). . . . . \(\left(1-\frac{2005}{5}\right)\)
c) C = \(\frac{8}{9}\). \(\frac{15}{16}\). \(\frac{24}{25}\). . . . . \(\frac{2499}{2500}\)
d) D = \(\left(1-\frac{1}{3}\right)\). \(\left(1-\frac{1}{6}\right)\). \(\left(1-\frac{1}{10}\right)\). . . . . \(\left(1-\frac{1}{780}\right)\)