伙计们。我想在我的 Ubuntu 18.04 lts 上安装 virtualbox，但是当我运行sudo apt update时，我得到： E: 列表文件 /etc/apt/sources.list (组件) 中格式错误的条目 53 E: 源列表无法被阅读。
这是该列表：
# deb cdrom:[Ubuntu 18.04 LTS _Bionic Beaver_ - Release amd64 (20180426)]/ bionic main restricted
# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.
deb http://lt.archive.ubuntu.com/ubuntu/ bionic main restricted
# deb-src http://lt.archive.ubuntu.com/ubuntu/ bionic main restricted
## Major bug fix updates produced after the final release of the
## distribution.
deb http://lt.archive.ubuntu.com/ubuntu/ bionic-updates main restricted
# deb-src http://lt.archive.ubuntu.com/ubuntu/ …