def chunk_sentences(sentences, chunk_size):
    """
    For a list of sentences, chunk sentences.
    Input:
      - sentences: list of single sentences
      - chunk_size: n sentences to be in one chunk
    Returns:
      - list of chunks, each containing n sentences
    """
    # Create empty target list for chunks
    chunks = []
    # Chunks into chunk size, and append to chunks list
    for i in range(0, len(sentences), chunk_size):
        chunks.append(' '.join(sentences[i:i+chunk_size]))  
        
    return chunks