已知<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202107/3b751d3b25514bec876427af5c1e59c1.png" />的z变换<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202107/6cd80d63c25f40f3930413d470be6bf3.png" />，<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202107/44a7b63737404bcfab64da5ae36635f0.png" />的收敛域为（ ）时是因果序列。 A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202107/5ef40bb06be14e9099b67ab2070ee216.png" /> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202107/293e604c21c54aff8f2f0bb128871ad7.png" /> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202107/f8db782ebecd4e808769625106929a3f.png" /> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202107/67575d32d53542f9926a431d42780f0f.png" />