Which two connections might cause the issue?

A user attempts a remote SSH connection to a newly installed ESXi 5.x host to execute some commands. The SSH connection attempts fails, through the user is able to receive a ICMP ping back from the host.
Which two connections might cause the issue? (Choose two)

A.
The shell timeout is set too low.

B.
The ParentRootLogin option is set to False.

C.
The SSH service is disabled on the host by default.

D.
The ESXi firewall blocks the SSH protocol by default.

Explanation:

Option A is incorrect:
Shell Timeout is disabled by default.

Page 87 from vsphere-esxi-vcenter-server-50-installation-setup-guide.pdf

Use the Direct Console User Interface (DCUI) to Enable Access to the ESXi Shell
The Direct Console User Interface (DCUI) allows you to interact with the host locally using text-based menus. You can use the Direct Console User Interface to enable local and remote access to the ESXi Shell.
NOTE Changes made to the host using the Direct Console User Interface, the vSphere Client, ESXCLI, or other administrative tools are committed to permanent storage every hour or upon graceful shutdown. Changes might be lost if the host fails before they are committed.
Procedure
1. From the Direct Console User Interface, press F2 to access the System Customization menu.
2. Select Troubleshooting Options and press Enter.
3. From the Troubleshooting Mode Options menu, select a service to enable.
* Enable ESXi Shell
* Enable SSH
4. Press Enter to enable the service.
5. (Optional) Set the timeout for the ESXi Shell. By default, the timeout for the ESXi Shell is 0 (disabled). The timeout setting is the number of minutes that can elapse before you must log in after the ESXi Shell is enabled. After the timeout period, if you have not logged in, the shell is disabled. NOTE If you are logged in when the timeout period elapses, your session will persist. However, the ESXi Shell will be disabled, preventing other users from logging in.
* From the Troubleshooting Mode Options menu, select Modify ESXi Shell timeout and press Enter.
* b Enter the timeout in minutes.
* c Press Enter.
6. Press Esc until you return to the main menu of the Direct Console User Interface.

Option B is incorrect:
The paremeter "ParentRootLogin" is only used in ESX no in ESXi

Option C is correct:
http://pubs.vmware.com/vsphere-50/index.jsp?topic=/com.vmware.vcli.getstart.doc_50/cli_jumpstart.3.6.html

Remote ESXi Shell Access with SSH
If Secure Shell is enabled for the ESXi Shell, you can run shell commands by using a Secure Shell client such as SSH or PuTTY.
Enabling SSH for the ESXi Shell
By default, remote command execution is disabled on an ESXi host, and you cannot log in to the host using a remote shell. You can enable remote command execution from the direct console or from the vSphere Client.

Option D is correct:
By default the service and ports are disable after installation.