Add a missing close backtick.
@@ -350,7 +350,7 @@ Output file:
`--left-file-join-columns LEFT_JOIN_COLUMNS ...` and `--right-file-join-columns RIGHT_JOIN_COLUMNS ...`
may be used to join on arbitrary sets of left and right file columns. It is necessary to use these
-options when processing quasi-KGTK files (`--mode=NONE`, `--left-mode=NONE`, `--right-mode=NONE).
+options when processing quasi-KGTK files (`--mode=NONE`, `--left-mode=NONE`, `--right-mode=NONE`).
### Memory Usage and stdin Limitation
