Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 23 to 27.

The Microscope

One of the most important inventions in the development of science and medicine was the microscope. It was (23) _________ the principle that light could be “ refracted ” or bent, by a glass lens. It was soon discovered that tiny objects could be magnified (24) _________ size when viewed through a glass lens that had been ground and polished in a specific (25) . _________ Although the principle was known to the Chinese as early as 1000 A. D, it was not until the 13th and 14th centuries in Europe (26) _________ it was put to practical use in the form of eyeglasses.
In Europe the first microscope was invented by brothers Zacharias and Hans Janssen, two Dutch eyeglass-makers, around 1590. They built a “compound” microscope, so called because of its two lenses. The most significant development and use of the microscope during this period, however, belongs to another Dutch optician, Antonie van Leeuwenhoek. Bom in Delft, Holland, he became skilled at (27) _________ very sharp and accurate magnifying lenses.