The correct answer is Option 3) i.e. stand down​. Key Points Let's look at the meanings of the given options: look down on- to regard as inferior. come across- to meet someone unexpectedly. take aback- to surprise. stand down- to wait; to stop pursuing or fighting. According to the context of the given sentence, the troops were ordered to stop fighting for some time. Hence from the given meanings, we find that stand down is the correct choice here. ​​​​Additional Information We should learn the words in a bunch if we want to enhance our vocabulary skills. Some phrasal verbs, with 'stand' as the main verb, are given below: stand for- to represent or mean, to support stand by- to be ready; to support stand up to- to defend or challenge stand out- to be noticeably better