根据《煤矿安全规程》的规定，井下主要水泵房、井下中央变电所、矿井地面变电所和地面通风机房的电话，应能与（）直接联系。
参考答案：矿调度室
An investment policy statement is important to the portfolio management process because it:（）
A. specifies allocations across assets and countries.
B. provides a clear understanding of the level of risk a client is willing to accept.
C. creates a record of the benchmark against which performance will be judged.
设随机变量X服从(0，2)上的均匀分布，Y服从参数λ=2的指数分布，且X，Y相互独立，记随机变量Z=X+2Y.
求E(Z)，D(Z)
