choose the best sentence that connects these two sentences

Question

     The sun shone so brightly in the afternoon that it heated the unshielded ice cream cart. The ice cream began to melt—it began slowly at first, but soon all of it became a slushy mess.

Choose the sentence that best connects these two sentences

Answer 1

I think the two sentences should read as follows:

The sun shone so brightly in the afternoon that it heated the unshielded ice cream cart. The ice cream began

to slowly melt, but soon all of it became a slushy mess.