while when as since

It is some time since Peter and I went on our second fossil hunt. On that day, while we were walking along the beach, we saw an interesting rock. We ran over to it. Peter hit the rock several times before it cracked open. We held our breath as the rock split into many pieces. I picked up a piece of the broken rock as Peter put his hammer into the rucksack.

As I lifted up the piece of rock, I could see something unusual in it. When Peter looked at it, he became very excited. Inside the rock were perfect fossils of prehistoric ferns. As I carefully put the rock into a box, Peter continued to look for more fossils. Before long, we had found two more fossils of ferns. Since that day, Peter and I have become keen fossil collectors.

Comment:
1. The conjunction is misplaced in the second sentence.
2. The verb, "put', is missing

---Fill in the blanks with while, when, as, since:-
(1)when
(2)while
(3)as

(4)When
(5)As
(6)While (Not at,carefully put the rock)
(7)Since

2013-11-03 14:31:26 補充：
Sorry for a correction:-(1)It is some time (since) adv. from then till now sometime ago.(7)(Since) that day,prep, at some time subsequent to.