Cho hình vẽ sau, biết a //b, \(\widehat {{A_1}} = {100^o}\). Tính \(\widehat {{B_1}},\widehat {{B_2}}\)

A. \(\widehat {{B_1}} = \widehat {{B_2}} = {100^o}\)

B. \(\widehat {{B_1}} = {100^o},\widehat {{B_2}} = {80^o}\)

C. \(\widehat {{B_1}} = {80^o},\widehat {{B_2}} = {100^o}\)

D. \(\widehat {{B_1}} = {100^o},\widehat {{B_2}} = {90^o}\)