You will be given a definition of a task first, then some input of the task.
In this task, you're given passages that contain mentions of names of people, places, or things. Some of these mentions refer to the same person, place, or thing. Your job is to write questions that evaluate one's understanding of such references. Good questions are expected to link pronouns (she, her, him, his, their, etc.) or other mentions to people, places, or things to which they may refer. Do not ask questions that can be answered correctly without understanding the paragraph or having multiple answers. Avoid questions that do not link phrases referring to the same entity. For each of your questions, the answer should be one or more phrases in the paragraph, and it should be unambiguous.

Passage: During the southern party's absence the relief ship Morning arrived, bringing fresh supplies. The expedition's organisers had assumed that the Discovery would be free from the ice in early 1903, enabling Scott to carry out further seaborne exploration and survey work before winter set in. It was intended that Discovery would return to New Zealand in March or April, then home to Britain via the Pacific, continuing its magnetic survey en route. Morning would provide any assistance that Scott might require during this period.This plan was frustrated, as Discovery remained firmly icebound. Markham had privately anticipated this, and Morning's captain, William Colbeck, was carrying a secret letter to Scott authorising another year in the ice. This now being inevitable, the relief ship provided an opportunity for some of the party to return home. Among these, against his will, was the convalescent Shackleton, who Scott decided "ought not to risk further hardships in his present state of health". Stories of a Scott-Shackleton rift date from this point, or from a supposed falling-out during the southern journey which had provoked an angry exchange of words. Some of these details were supplied by Armitage, whose relationship with Scott had broken down and who, after Scott, Wilson and Shackleton were all dead, chose to reveal details which tended to show Scott in a poor light. Other evidence indicates that Scott and Shackleton remained on generally good terms for some while; Shackleton met the expedition on its return home in 1904, and later wrote a very cordial letter to Scott.
Output:
What was the last name of the man that provided the secret letter the captain was carrying?