------
## 最终结论
```python
def concatenate_elements(lst):
    return ' '.join(lst)

# Test cases
assert concatenate_elements(['hello','there','have','a','rocky','day'] ) == 'hello there have a rocky day'
assert concatenate_elements([ 'Hi', 'there', 'How','are', 'you'] ) == 'Hi there How are you'
assert concatenate_elements([ 'Part', 'of', 'the','journey', 'is', 'end'] ) == 'Part of the journey is end'
```