(begin{array}{l}a),,A = frac{{ – 3}}{{13}} – frac{7}{{17}} + frac{{ – 5}}{{19}} + frac{{ – 10}}{{13}} + frac{{24}}{{17}} – frac{{14}}{{19}},,\,,,,,,A = frac{{ – 3}}{{13}} + frac{{ – 7}}{{17}} + frac{{ – 5}}{{19}} + frac{{ – 10}}{{13}} + frac{{24}}{{17}} – frac{{14}}{{19}},\,,,,,,A = left( {frac{{ – 3}}{{13}} + frac{{ – 10}}{{13}}} right) + left( { – frac{7}{{17}} + frac{{24}}{{17}}} right) + left( {frac{{ – 5}}{{19}} – frac{{14}}{{19}}} right)\,,,,,,A = frac{{ – 13}}{{13}} + frac{{17}}{{17}} + frac{{ – 19}}{{19}},,,,,\,,,,,,A = ( – 1) + 1 + ( – 1),,,,,,,,,,,,\,,,,,A = -1,,,,end{array})
Chọn D