Montags and Clarisse's realtionship is weird. If she had not died I think they would have become a lot closer throughout the book. Clarisse seemed to bring out a different side of Montag. They way she would ask him questions and make things for him.
JKS stands for Java KeyStore. It is a repository of certificates (signed public keys) and [private] keys. You can export a certificate stored in a JKS file into a certificate file. You can use the keytool utility found in Java distributions to maintain your JKS trust and key repositories.
In this case, try to re-select the appropriate application. Right-click on the .JKS file, and then select from the menu the option Open With ... and Choose default program . Now select one of the installed application from the list above and try again. Programs that will open the .JKS file.