A. Parfois, ce genre de coïncidences a tendance à s'enchaîner.
The example A uses "a" instead of "ont", so the "avoir" here agrees with the singular noun "ce genre", not with the "coïncidences".
B. Quel dommage que ce genre de soirées soient si rares.
On the other hand, the example B uses "soient" instead of "soit", so the "être" here agrees with the plural noun "soirées", not with the "ce genre". }
The verb following the phrase "ce genre de" should be in the singular or the plural? Which one is actually correct?