TASK DEFINITION: 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.
PROBLEM: Sentence 1:Content is free of charge for professionals and others . Sentence 2:but registration is required .

SOLUTION: but

PROBLEM: Sentence 1:However , their stories , composed in verse form , were not written down until the subsequent Sassanian period . Sentence 2:In fact , there is no known Parthian - language literature that survives in original form , since it was written down in the following centuries .

SOLUTION: in fact

PROBLEM: Sentence 1:Moreover , elevation above this threshold in GAP43 mice can enhance learning and also facilitate a physiological model of learning , long - term potentiation ( LTP ) . Sentence 2:However , further enrichment beyond a certain level can be devastating to cognitive functions .

SOLUTION:
however