Error in the language is a human fact. Language error is an ‘unsuccessfully bit of language’. The occurrence of errors, while speaking or writing language may be due to the lack of attention on the part of a learner. It should be noted that:

• While interlingual errors are caused mainly by mother tongue interference, intra- 'lingual or developmental errors originate in the following factors: simplification, overgeneralization, hyper- correction, faulty teaching, fossilization, avoidance, inadequate learning (partial knowledge), and false concepts hypothesized. 
• For example, ‘Giving their examination’ is grammatically wrong. The correct sentence will be – “The students are taking their examination.” This error developed because of the literal translation from Hindi to English.
• Making errors is natural in case one has partial knowledge of the subject matter. The same goes true for language learning as well.
• Errors made by learners at the level of word, phrase, and sentence are called reading errors.

Hence, from the above-mentioned points, it becomes clear that the correct sentence will be – “The students are taking their examination.”