Answer:
he fears that he will be left to answer for Kurtz's brutal behavior
Step-by-step explanation:
We can make this assertion because the Manager does not view Kurtz's method as effective. In fact, we are told, he viewed it as an "...unsound method". Hence, since the Manager is superior to Marlow, we can expect him to fear been reprimanded by the Manager. In other words, fears that he will be left to answer for Kurtz's brutal behavior.