In this task, you are given two sentences in the English language (Sentence 1 and Sentence 2). Your task is to identify the connecting word between the two sentences.
One example: Sentence 1:A suicide car bomber detonated his bomb as he attempted to drive an SUV into a Somali military camp . Sentence 2:However the vehicle exploded at the entrance when police guards opened fire on the insurgent driving the vehicle .
Solution is here: however
Explanation: The above sentence is connected by the word 'however'.

Now, solve this: Sentence 1:Content is free of charge for professionals and others . Sentence 2:but registration is required .
Solution:
but