Identify the complex sentence from below.

• Complex sentence: 
- যে sentence এ একটি Principal clause এবং এক বা একাধিক Subordinate clause থাকে, তাকে Complex sentence বলে। 
- Complex sentence এর subordinate clause এর শুরুতে সাধারণত if, though, although, as, because, since, so that, that, until, till, unless, when, why, who, which, where, how, before, after, whether, while বসে।
- সুতরাং, নিয়মানুযায়ী -Although she was tired, she stayed up to finish her project হচ্ছে complex sentence.

• অন্য অপশন গুলোর মধ্যে - 
ক) They went for a walk in the park - Simple sentence.
গ) Read attentively - Imperative sentence.
ঘ) He went to the store and bought some groceries - Compound sentence.