单项选择题 In many simple organisms, including bacteria and various protists, the life cycle is completed within a single generation: an organism begins with thefissionof an existing individual; the new organism grows to maturity; and it then splits into two new individuals, thus completing the cycle.

单项选择题 The two fanatic Puerto Rican nationalists who tried to assassinate Harry Truman in 1950 attacked him when he was living across the street in Blair House while the White House was beingrenovated.

单项选择题 Some industrial workers were trying, quietly and peacefully, to create a network of free trade unions, modeled presumably on Poland’s famous Solidarity, which wasan anathemato the regime.