For the purpose of the Rules, except where otherwise required, the term ______.A. vessel includes seaplanesB. seaplane includes non-displacement craftC. vessel engaged in fishing includes a vessel fishing with trolling linesD. vessel restricted in her ability to maneuver includes fishing vessels

本题考查国际海上避碰规则（COLREGs）中对术语“vessel”的定义。核心思路是明确规则中对“vessel”的范围界定，需结合规则第3条内容判断选项。关键点在于区分不同航行器的分类，例如水上飞机（seaplanes）是否被包含在“vessel”中，以及相关条款的特殊说明。

选项分析

A. vessel includes seaplanes

正确。根据COLREGs第3条定义，“vessel”一词明确包含seaplanes（水上飞机），这是规则中的基础条款。

B. seaplane includes non-displacement craft

错误。seaplane本身属于vessel的子类，而non-displacement craft（如气垫船）属于另一类别，二者是并列关系，而非包含关系。

C. vessel engaged in fishing includes a vessel fishing with trolling lines

错误。虽然 trolling lines（拖钓）属于捕鱼方式，但规则中“从事捕鱼的船舶”特指使用渔具可能限制操纵能力的船舶，而trolling lines是否被明确包含需具体条款支持，此处未直接对应。

D. vessel restricted in her ability to maneuver includes fishing vessels

错误。根据规则第3条，“操纵能力受限的船舶”特指从事清除水雷、潜水作业等船舶，捕鱼船不属于此类别，应归为“从事捕鱼的船舶”。