Qemuパッケージのインストール中にエラーが発生しました

私の仮想マシンDebian 9にQemuをインストールしたいのですが、インストールできません。誰でもこの問題を解決できれば役に立ちます。 Debian 9 の vdi ファイルは当社が提供しています。

root@stretch:~# sudo apt-get update
-su: sudo: command not found

root@stretch:~# apt-get install sudo
E: Conflicting values set for option Trusted regarding source http://linux.dropbox.com/debian/ stretch
E: The list of sources could not be read.
E: Conflicting values set for option Trusted regarding source http://linux.dropbox.com/debian/ stretch
E: The list of sources could not be read.

root@stretch:~# apt-get install qemu
E: Conflicting values set for option Trusted regarding source http://linux.dropbox.com/debian/ stretch
E: The list of sources could not be read.
E: Conflicting values set for option Trusted regarding source http://linux.dropbox.com/debian/ stretch
E: The list of sources could not be read.

ヘッダー -n 1000 /etc/apt/sources.list /etc/apt/sources.list.d/*

root@stretch:~# head -n 1000 /etc/apt/sources.list /etc/apt/sources.list.d/*
==> /etc/apt/sources.list <==
# 

# deb cdrom:[Debian GNU/Linux 9.4.0 _Stretch_ - Official amd64 DVD Binary-1 20180310-11:21]/ stretch contrib main

# deb cdrom:[Debian GNU/Linux 9.4.0 _Stretch_ - Official amd64 DVD Binary-1 20180310-11:21]/ stretch contrib main

# Line commented out by installer because it failed to verify:
# deb http://security.debian.org/debian-security stretch/updates main contrib
# Line commented out by installer because it failed to verify:
# deb-src http://security.debian.org/debian-security stretch/updates main contrib

# stretch-updates, previously known as 'volatile'
# A network mirror was not selected during install.  The following entries
# are provided as examples, but you should amend them as appropriate
# for your mirror of choice.
# 
# deb http://deb.debian.org/debian/ stretch-updates main contrib
# deb-src http://deb.debian.org/debian/ stretch-updates main contrib
deb http://deb.debian.org/debian/ stretch main contrib non-free


==> /etc/apt/sources.list.d/backports-stretch.list <==
deb http://http.debian.net/debian stretch-backports main contrib non-free

==> /etc/apt/sources.list.d/download_docker_com_linux_debian.list <==
deb [arch=amd64] https://download.docker.com/linux/debian stretch stable

==> /etc/apt/sources.list.d/dropbox.list <==
deb [arch=i386,amd64] http://linux.dropbox.com/debian stretch main

==> /etc/apt/sources.list.d/httpredir_debian_org_debian.list <==
deb http://httpredir.debian.org/debian stretch main contrib non-free

==> /etc/apt/sources.list.d/linux_dropbox_com_debian.list <==
deb [trusted=yes] http://linux.dropbox.com/debian stretch main

==> /etc/apt/sources.list.d/pike_zilogic_com_zdrive_debian_repo.list <==
deb [trusted=yes] https://pike.zilogic.com/zdrive/debian/repo/ wheezy main

==> /etc/apt/sources.list.d/security_debian_org_debian_security.list <==
deb http://security.debian.org/debian-security stretch/updates main

==> /etc/apt/sources.list.d/shark_zdrive_debian_repo.list <==
# deb [trusted=yes] https://pike.zilogic.com/zdrive/debian/repo/ wheezy main