Consider the following series:
sera
| a | 1 |
| b | 2 |
serb
| x | 10 |
| y | 20 |
| a | 100 |
| b | 20 |
Choose the correct value of sera after execution of the following statement sera.add(serb, fill_value=0)
1
\(\begin{array}{ll} \mathrm{a} & 1 \\ \mathrm{b} & 2 \\ \mathrm{x} & 10 \\ \mathrm{y} & 20 \\ \mathrm{a} & 100 \\ \mathrm{b} & 20 \end{array}\)
2
\(\begin{array}{ll} \mathrm{a} & 101 \\ \mathrm{b} & 22 \\ \mathrm{x} & 10 \\ \mathrm{y} & 20 \end{array}\)
3
\(\begin{array}{r} 101 \\ 22 \\ 110 \\ 120 \end{array}\)
4
\(\begin{array}{ll} \mathrm{a} & 101 \\ \mathrm{b} & 22 \\ \mathrm{x} & \mathrm{NaN} \\ \mathrm{y} & \mathrm{NaN} \end{array}\)