Causal
strong strength
Narrative Connection
How these two moments in the story relate
From
Vana reveals the acid plan
S6E22
·
The Krotons Part 4
To
Sabotage fails but reveals Krotons' weakness
S6E22
·
The Krotons Part 4
Why These Connect
The narrative assertion
"Vana explains that she and Thara remained to prepare sulphuric acid for the Doctor. Later, Vana delivers a small sample to the Doctor."
About Causal Connections
A directly causes B. The first event sets forces in motion that produce the second. These are the load-bearing connections of plot--remove one and the story structure collapses.