Run-On sentence.. need help

[krazygmat]

1)Are these sentences a run-on:
The old firefighter stood over the smoking ruins, his senses alert to any sign of another flare-up.
The old firefighter stood over the smoking ruins, he was alert to any sign of another flare-up.
kindly cite reasons.

2) Though I studied hard, yet I failed.
Is the usage of subordinate conjunction and co-ordinate conjunction incorrect as in the sentence above.

Kindly Explain your answers in detail.
Thanks.

[RonPurewal]

1)Are these sentences a run-on:
The old firefighter stood over the smoking ruins, his senses alert to any sign of another flare-up.
The old firefighter stood over the smoking ruins, he was alert to any sign of another flare-up.
kindly cite reasons.

the former of these is a legitimate sentence. the modifier that follows the comma is called an "absolute phrase" -- a modifier that will be totally unfamiliar from spoken language (since it's actually impossible to speak out loud!), but with which you should be familiar because it is actually fairly common on the test.

for more on this type of modifier, see this thread (and the other threads that are referred within it):
http://www.beatthegmat.com/sound-can-tr ... tml#244780

the latter is a run-on sentence; the part before the comma is a complete sentence all by itself, and the part after the comma is also a complete sentence all by itself. although you would be allowed to do that with a semicolon, you are not allowed to do so with a comma. this incorrect construction is called a "comma splice", and is probably the most common type of run-on sentence.

2) Though I studied hard, yet I failed.
Is the usage of subordinate conjunction and co-ordinate conjunction incorrect as in the sentence above.

yeah, you can't have both of those.

the sentence would be correct if you took out "yet", and it would also be correct if you took out "though". you just can't have a construction in which two conjunctions play the same role ("though" and "yet" both signify contrast), so this sentence is unacceptably redundant.