EXPLAINS, IS
The tour guide EXPLAINS that either candles or a lantern IS used to see into the tomb.
Tour guide is singular. Therefore, verb used must be in singular form.
Lantern is singular and it is the nearest subject of the verb. Thus, the verb must also be in singular form.
I RUNNO ASK UR SELF SELF SELF SELF
The only word out of these four which has an obvious negative connotation is C) harangue. That word means <em>to lecture somebody in an aggressive manner</em>, which is negative.
The other words have neutral connotation.