α粒子散射实验结果表明（   ）

A．原子中绝大部分是空的

B．原子中全部正电荷都集中在原子核上

C．原子内有中子

D．原子的质量几乎全部集中在原子核上

According to the Global Investment Performance Standards (), which of the following statements is most accurat.e about composites used for performance presentation of a investment management firm（）

A. Composites must include one or more portfolios managed to a similar investment strategy, objective or mandate.

B. Composites must include all discretionary and non-discretionary portfolios managed to a similar investment strategy, objective or mandate.

C. Composites must include all fee-paying and non-fee paying portfolios managed to a similar investment strategy, objective or mandate.