英文tenseSincecomputerswerefirstintroducedtothepublicintheearly1980's,technology(change)haschangedagreatdeal.Thefirstcomputers(be)weresimplemachinesdesignedforbasictasks.They(have,not)didnothavemuchmemoryandthey(

Question

英文tense
Since computers were first introduced to the public in the early 1980's,technology (change) has changed a great deal.The first computers (be) were simple machines designed for basic tasks.They (have,not) did not have much memory and they (be,not) very powerful.Early computers were often quite expensive and customers often (pay) thousands of dollars for machines which actually (do) very little.Most computers (be) separate,individual machines used mostly as expensive typewriters or for playing games.
为什麼最后3个答案要用过去式.不是现在完成式吗?

Answer 1

一般过去时描述过去的动作,现在完成时则强调过去的动作对现在造成影响.
上文中,
customers often (pay) thousands of dollars 与 which actually (do) very little,动作 paid 与 did little 对现在的影响不大,用一般过去时.
Most computers (be) separate,系表中的 were 也只虽对当时电脑形态的描述,跟现在没有关系,不用强调.
所以以上三处均用一般过去时.