I ate __________ sandwich while I was waiting for _______ 20:08 train.

A．the; a

B．the; the

C．a; the

D．a; a

在数列{a_n}中,若对任意的n均有a_n+a_n+1+a_n+2为定值(n∈N^*),且a₇=2,a₉=3,a₉₈=4,则此数列{a_n}的前100项的和S₁₀₀=　　　　.