The correct answer is Only 1. Key Points A connector is a thing that links two or more things together. The sentence says that We should not be afraid of difficulty in life as difficult roads often lead to beautiful destinations. So, the connector which can connect these two sentence is 'Because' which is used when we are focusing on the reason of doing a certain thing. ​Example - I got good marks in the examination because I prepared for it very well. So, 'Because' is the correct word. So, the correct sentence is - Don't fear difficulty in life because difficult roads lead to beautiful destinations. Additional Information The types of connectors in English are: coordinating conjunctions, correlative conjunctions, subordinating conjunctions, conductive adverbs and prepositional phrases. ​'Since' is used to refer to a point after a specific time or an event in the past. Or it can refer to a particular point beginning sometime in the past and continuing until the present time. It's been many years since I rode a bicycle.​ ​'Either...or' is used to indicate that there are only two options or that both of the two options are acceptable or equivalent. It is a correlative connector. He can play either tennis or badminton.