sporadic

这座城市的某些地区只有零星的网络信号覆盖。

Some areas of this city have only ___sporadic network coverage.

下午不时出现的零散阵雨迫使婚礼仪式搬到了室内。

___Sporadic showers throughout the afternoon forced the wedding ceremony indoors.

他学习法语的努力零零星星，每次最多坚持不过两周。

His ___sporadic attempts at learning French never lasted more than two weeks at a time.