Answer:
1) Test tube 3, and 1.
2) Test tube 4, and 2.
3) Test tube 3.
4) Test tube 1.
Step-by-step explanation:
Test tubes 4, and 2 don't react because the sodium carbonate (NaCO3) needs to become sodium hydrogen carbon (NaHCO3) to form a possible reaction. NaCO3 + C6H8O7 → No reaction.
NaHCO3 + C6H8O7 → NaC6H7O7 + H2O + CO2