A.
growing number of people who purchase plane tickets online, airline executives
are convinced that, just as one-third of bank customers still prefer human
tellers to automatic teller machines, many travelers will

B.
growing number of people who purchase plane tickets online, airline executives
are convinced, just as one-third of bank customers still prefer human tellers
to automatic teller machines, that many travelers would

C.
growing number of people purchasing plane tickets online, airline executives
are convinced, just as one-third of bank customers still prefer human tellers
as compared to automatic teller machines, many travelers will

D.
fact that the number of people purchasing plane tickets online is growing,
airline executives are convinced, just as one-third of bank customers still
prefer human tellers as compared to automatic teller machines, that many
travelers would

是不是convice 后面必须加that？

E.
fact that the number of people who purchase plane tickets online are growing,
airline executives are convinced that, just as one-third of bank customers
still prefer human tellers compared with automatic teller machines, many
travelers would

答案是E吗？？

但是the number of....后面谓语动词不是应该用is吗？？

that应该放在convinced后面,将just as one-third of bank customers still prefer

human tellers as compared to automatic teller machines用来修饰convinced的原因

再加are convinced that will/would 应该是现在时态.

选a

 应为just as是从句中的组成部分

所以必须放在that后面