[译]人体保持着一个适宜于细胞正常活动的内部环境。
[误] The human body maintains an internal surroundings favorable to normal cell activity.

[正]The human body maintains an internal environment favorable to normal cell activity.
[注]表示“内部环境”时只用 environment；surroundings 与 environment 作“外界环境”解时，可以互换使用。如：A plant will often grow differently in a different environment (surroundings)。每种植物在不同环境中常常生长得不一样。