What first triggers the calculation of the Additional Child Tax Credit.

A$-$ Due to tax liability limits$,$ the taxpayer did not receive the mazimum CTC for which they were eligiblr.

B$-$ more than two children lived with the taxpayer

C$-$ the taxpayer's modified AGI was more than $15\%$ over the threshold

D$-$ the taxpayer's modified AGI exceeds $$15,300.$