The nature of viruses made them (1) impossibly to detect for many years, (2) even after bacteria had (3) been discovered and (4) studied.

(a)  

Some of (1) American’s best universities (2) have accepted (3) an (4) unusually low percentage of students for admission.

(a)  

Either a (1) larger location will be found, (2) and the (3) annual conference will (4) have to be rescheduled.

(a)  

CNN reported that (1) weakened and crippled children (2) were infected from the diseases and other (3) epidemics that are (4) hard preventable.

(a)  

(1) Even if the papyrus had (2) its drawbacks in the Western world, the papyrus rolls were infinitely (3) superior to books (4) made from bamboo.

(a)  

Hares (1) frequently are often mistake for rabbits, (2) but hares are larger and (3) usually have longer legs and ears than (4) do rabbits.

(a)  

(1) According to a survey (2) conducting by the fielding Institute, advertising on the internet (3) accounted for 10% of total advertising.

(a)  

(1) Recycle does not cost (2) anything, takes only (3) a little extra time, and can make an amazing difference (4) to environment.

(a)  

Water should not (1) allow to stand next to a house because (3) it will (3) eventually seep (4) through the foundation walls.

(a)  

(1) Unless the Bangkok can prevent floods or (2) does not contribute much during the dry season, (3) its constructions (4) will not be necessary.

(a)  

(1) The revival of the ferry services to Seawise Island (2) were initially viewed as a foolish notion by (3) many, but it returned out to (4) be profitable.

(a)  

Please (1) remove all objects from your window and balconies (2) before April 16 and avoid (3) touching the building’s outside walls while painting (4) is done.

(a)  

(1) Although the main audience of (2) children’s literature (3) are children, many books are also (4) enjoyed by teenagers and adults.

(a)  

Drinking coffee always has a (1) stimulating effect (2) with the central nervous system (3) as it contains with (4) stimulant like caffeine.

(a)  

Normally, winter draws (1) the most amount of tourists to the Northern of Thailand as they like (2) experiencing the famous mountain top to admire the (3) breathtaking scenery and its rich and flawless (4) flora and fauna.

(a)