Answer:
A. If it is warm outside, then it is summer
Explanation:
statement "If it is summer, then it is warm outside" : warm=summer
A. If it is warm outside, then it is summer. : warm = summer ✓
B. If it is not warm outside, then it is summer. : not warm = summer x
C. If it is warm outside, then it is not summer. : warm =not summer x
D. If it is not warm outside, then it is not summer. : not warm = not summer x