Answer:
The speaker who does not contribute to the poem is:
D.the mother of the dead man
Explanation:
Let's take a look at the poem:
<em>Nobody heard him, the dead man, </em>
<em>But still he lay moaning:
</em>
<em>I was much further out than you thought </em>
<em>And not waving but drowning.
</em>
<em>
</em>
<em>Poor chap, he always loved larking
</em>
<em>And now he’s dead
</em>
<em>It must have been too cold for him his heart gave way, </em>
<em>They said.
</em>
<em>
</em>
<em>Oh, no no no, it was too cold always </em>
<em>(Still the dead one lay moaning) </em>
<em>I was much too far out all my life </em>
<em>And not waving but drowning.</em>
<em />
There are three speakers contributing to the poem: the narrator, the drowned man himself, and the friends of the dead (drowned) man. The narrator is the one letting us know that the dead man is laying, moaning:
<em>Nobody heard him, the dead man, </em>
<em>But still he lay moaning</em>
<em />
The drowned man is the one explaining that he was asking for help, not waving. His gesture was most likely misunderstood, which is why no one rescued him:
<em>I was much further out than you thought </em>
<em>And not waving but drowning.
</em>
<em>[...]</em>
<em>Oh, no no no, it was too cold always </em>
<em>[...] </em>
<em>I was much too far out all my life </em>
<em>And not waving but drowning.</em>
<em />
His friends are only referred to as "they". As the man lies, dead, they talk about what a good person he was - which is a typical reaction of people in general when someone dies:
<em>Poor chap, he always loved larking
</em>
<em>And now he’s dead
</em>
<em>It must have been too cold for him his heart gave way, </em>
<em>They said.
</em>
<em />
At no point the mother of the dead man is mentioned, nor does she contribute to the poem.