Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer that best fits the blank space in the following passage.

Taking piano lessons and solving math puzzles on a computer significantly improve specific math skills of elementary schoolchildren, according to a new study. The results, (26)_______ were published in the journal Neurological Research, are the latest in a series that links musical training to the development of higher brain functions.
Researchers worked with 135 second-grade students at a school in Los Angeles after (27)_____ a pilot study with 102 students. Children that were given four months of piano training as well as time playing with newly designed computer software scored 27 percent higher on math and fraction tests than (28)________ children.
Piano instruction is thought to enhance the brain's "hard wiring" for spatial-temporal reasoning, or the ability to visualise and transform objects in space and time, says Professor Gordon Shaw, who led the study. At the same time, the computer game allows children to solve geometric and math puzzles that boost their ability to (29)______ shapes in their mind.
The findings are significant (30)_____ a grasp of proportional math and fractions is a prerequisite to math at higher levels, and children who do not master these areas of math cannot understand more advanced math that is critical to high-tech fields.