What is the assimilating pair in وَقَالَتْ طَائِفَةٌ?

Idghām: Types, Complete/Incomplete Assimilation and the Definite Article

• Lām and tāʾ
• Qāf and alif
• Tāʾ and ṭāʾ
• Fāʾ and tāʾ marbūṭah