the difficulty of giving a distinct definition separating plants from other life forms
We understand from the passage that protoplasm is a simple life form
is a method of grouping life forms
is a separate life form
contains cells
is the distinctive characteristic of plants
The current method of classifying life forms involves separating the plant and animal kingdoms
58 ICE-BORG Because of his imperturbable manner, both on and off the tennis court, and his relentless ground strokes, Bjom Borg was dubbed Ice-Borg by his opponents on the professional tennis circuit. Borg won his first tournament when he was 11. In four years, he won all the world's junior titles, and became the first of the teenage wonders to achieve world-class status. He dropped out of school when he was in the ninth grade, at the age of 15, and qualified for the Swedish Davis Cup team, becoming the youngest player ever to win a cup match. This was his first encounter with team captain Lennart Bergelin, who later became Borg's full-time coach. In 1975 Borg's three match victories, including doubles, brought Sweden its first Davis Cup. In his first decade in competitive tennis, the goldenhaired Swede broke more records than anyone else in the history of tennis. Borg was only 26 when he retired, and he failed in his attempt eight years later to make a comeback with his old wooden racket - made obsolete by the oversized models that are now used in the game.