quizzes: expand all 35 quizzes to 15 questions each

OPS-1 through OPS-10, OS-2, OS-3 went from 5 → 15.
OS-1, OS-4 through OS-11, SEC-1 through SEC-11, TRB-1 through TRB-4 went from 7 → 15.
Questions cover exam-weight scenarios not duplicated from original content.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

quizzes/OS-9-quiz.md

@@ -56,6 +56,62 @@ B. `mount`
 C. `sudo`  
 D. `find`  
 
+8. Which command shows the current working directory in Linux?
+
+A. `ls`  
+B. `cd`  
+C. `pwd`  
+D. `cat`  
+
+9. Which command changes file ownership in Linux?
+
+A. `chmod`  
+B. `chown`  
+C. `grep`  
+D. `find`  
+
+10. Which Linux command installs a package on Red Hat/CentOS-based systems?
+
+A. `apt install`  
+B. `brew install`  
+C. `dnf install` or `yum install`  
+D. `dpkg --install`  
+
+11. Which command searches for text inside files in Linux?
+
+A. `man`  
+B. `df`  
+C. `grep`  
+D. `mount`  
+
+12. Which file in Linux defines where file systems are mounted at boot?
+
+A. `/etc/passwd`  
+B. `/etc/shadow`  
+C. `/etc/hosts`  
+D. `/etc/fstab`  
+
+13. Which Linux command shows disk usage for a specific directory?
+
+A. `df -h`  
+B. `du -sh /path`  
+C. `top`  
+D. `man`  
+
+14. Which permission string means owner can read/write/execute, group can read/execute, others can read only?
+
+A. `rwxrwxrwx`  
+B. `rwxr-xr--`  
+C. `rw-rw-rw-`  
+D. `r--r--r--`  
+
+15. Which command shows who is currently logged in to a Linux system?
+
+A. `ps aux`  
+B. `df`  
+C. `w` or `who`  
+D. `grep`  
+
 ## Answer Key For Instructor
 
 1. C
@@ -65,4 +121,12 @@ D. `find`
 5. B
 6. D
 7. A
+8. C
+9. B
+10. C
+11. C
+12. D
+13. B
+14. B
+15. C