BrX −
,RbX
+
,SeX
2−
,SrX
2+
the trend in radii for these ions

No because scientist are still changing there mines today so they are not correct to this day

The answer is d, you can easily test a theory! hope i you : )

The  moon has  insufficient gravity to retain an  atmosphere. we conclude that the moon has no atmosphere  because its gravitational field is too weak to  have  retained any  atmosphere  that it had over times comparable to the age of the solar system.