_______ by keeping down costs will Power Data hold its advantage over other companies.

Only  

Just 

 Still  

Yet

考查倒装句式。句意：只有通过降低成本，Power Data才能比其它公司更有优势。A只有；B仅仅；C仍然；D然而。Only加副词、介词短语或时间状语，放句首时，用部分倒装。故选A。

My mom suggest that we           eat out for a change this weekend.

should

might

could

would

考查虚拟语气。句意：我妈妈建议我们这周末出去吃饭换换口味。suggest作“建议”时，后面的宾语从句要用虚拟语气（should）+动词原形。故选A项。

The law           equal rights for men and women.

permits

confirms

persevers

guarantees

考查动词辨析。句意：这个法律确保了男女权利平等。A.permit允许；B.confirm证实，证明；C.persever坚持；D.guarantee保证，担保。分析句意可知，空格处为动词做谓语，其主语为the law,为单数则谓语动词用第三人称单数形式。又因the law作用是保证公平。故选D项。

So difficult __________ it to work out the problem that I decided to ask Tom for advice.

 I did find 

did I find

 I have found  

have I found

句子使用的基本句式为so…that…结构。按英语语法，当该结构的so…置于句首时，其后的句子(主句)要用倒装语序，如：So loudly did he speak that even people in the next room could hear him. 他讲话声音那么大，隔壁屋里的人都听得见。

Really? You        twice the price to buy the book!

paid

took

spent

cost

考查动词词义辨析。句意：真的吗？你付了2倍的价格买这本书！四个动词都有“花费”的意思，但用法不同。pay的主语通常是人，常用结构是 sb pay (money) for sth;take作“花费”时讲常用于固定句型 It takes/took sb (money/time)to do sth做某事花费某人（金钱/时间）；spend的主语通常是人 sb spend...on sth 或sb spend ...(in) doing sth;cost的主语通常是物，sth cost sb (money)意为“某物花了某人多少钱。本题主语是人，结合句意和后文to buy the book，空格处应填pay。故选A项。