bothers me is that I can't keep my mind on the task, but on personal gains or losses.

What

It

That

One

考查主语从句连接词。句意：困扰我的是我不能专注于任务，而是专注于个人得失。此处为主语从句，从句中缺少主语，结合句意表示“困扰我的是”应用what。故选A项。

I found _____ convenient to shop online at home .

it’s 

that

it

that was

考查强调句。句意：我发现在家网购很方便。这里it指代后面的to shop online。其中的强调句式是：主语+find it +形容词+to do，意为主语发现做某事是...的，故选C。

I drink a cup of coffee           ; but usually I take tea.

frequently

often

constantly

occasionally

考查副词词义辨析。句意：我偶尔喝一杯咖啡，但我通常喝茶。A. frequently频繁地；B.often经常地；C.constantly连续不断地；D.occasionally偶尔地。but 表转折关系；根据后半句的usually,前面用occasionally,与usually意思相对。故选D项。

The old rules have to be          because they only applied to the circumstances that existed when they were made a hundred years ago.

developed

established

observed

revised

考查动词的辨析。句意：老的规则需要被修改因为它们只适合一百年制定时的状况。A.develop发展；培养；B.establish建立；C.observe观察；D.revise修改，由because they only applied to 可知它只适用于以前，需要修改。故选D项。

The question of           English will keeping on changing in the future is easy         .

if; to answer

whether; to be answered

if; to be answered

whether; to answer

考查宾语从句和非谓语动词。句意：英语将来是否会继续变化这个问题很容易回答。第一空为宾语从句，从句中不缺少成分，表示“是否”，应用whether，if 引导的宾语从句不能充当介词的宾语，故排除A和C；第二空，这是be +性质形容词+不定式结构，这种结构中形容词说明不定式的特性，句子的主语是不定式的逻辑宾语。故选D项。

I_____you can finish the exam in two hours.

does believe

do believe

did believed

do believed

句意：---我确实相信两个小时内能完成考试。这里用来强调，在谓语动词前加助动词do表示强调。句子的主语是第一人称，所以位于动词不能用单数，故排除A；did后用动词原形；do后用动词原形，故选B。