/usr/bin/xwininfo, xwininfo
Explanation:
The xwininfo command is a utility for displaying information about windows in X. It can show various attributes of a window, such as its location, size, depth, border width, visual class, colormap, map state, and event masks. The -metric option specifies that all dimensions should be displayed in metric units (millimeters) rather than pixels. By issuing the xwininfo -metric command and then clicking on a window, the administrator can determine the geometry of that window, including the decorations, in millimeters. References:
* xwininfo(1) - Arch manual pages
* [command line -

An SSH host key is a cryptographic key used for authenticating computers in the SSH protocol. Host keys are key pairs, typically using the RSA, DSA, or ECDSA algorithms. Public host keys are stored on and/or distributed to SSH clients, and private keys are stored on SSH servers. Each host (i.e., computer) should have a unique host key. Host keys are used for authentication towards the connecting client, analogous to user SSH keys. Host keys are generated using asymmetric encryption algorithms like RSA, DSA, or ECDSA algorithms12. When a client connects to the host, the host sends its public host key to the client, and the client verifies that the host key matches the one stored in its known hosts file. If the host key is unknown or has changed, the client will display a warning and prompt the user to accept or reject the host key. This is to prevent man-in-the-middle attacks, where an attacker intercepts the connection and pretends to be the legitimate host. The other options are either incorrect or irrelevant to the purpose of an SSH host key. References:
* What is an SSH Host Key & How are They Configured?, What are SSH Host Keys? section
* SSH Host Key Management Demystified, What are SSH host keys? section
* What is SSH host key - omnisecu.com, first paragraph

SPICE is a protocol that allows users to access graphical applications on a remote host, such as a virtual machine or a server, using a client program. SPICE also supports connecting local USB devices to remote applications, such as printers, scanners, or flash drives, using a feature called USB redirection. SPICE does not replace Xorg as the local X11 server, nor does it allow downloading and locally installing applications or uploading and running binary programs from a remote machine. These are features that are provided by other tools, such as SSH, SCP, or RDP. Reference:
Features - spice-space.org
SPICE - Wikipedia
SPICE Model ＜What is SPICE?＞ | Electronics Basics | ROHM