Two extra lines are being added to the end of the algorithm in Figure 1.

Fill in the gaps so the output from the new final line will be the string 'Carbongen'.

temp ← SUBSTRING( _ _ _ _ _ , _ _ _ _ _ , gas2)

OUTPUT elements[ _ _ _ _ _ ] + temp

Figure 1

1  elements ← ['Helium', 'Oxygen', 'Carbon']
2  gas1 ← 'Nitrogen'
3  gas2 ← 'Hydrogen'
4  OUTPUT gas1
5  OUTPUT LEN(elements)
6  temp ← SUBSTRING(0, 3, gas1)
7  OUTPUT temp

SUBSTRING returns part of a string from a start index to an end index inclusive. For example, SUBSTRING(1, 4, 'computer') will return the string 'ompu'.