第三人称单数： stiffens
过去式： stiffened
过去分词： stiffened
现在分词： stiffening

Glue the ends of the ribbons to stiffen them up and make threading easier .

用胶水使丝带的两端变硬，可以让孩子们在穿洞的时候更容易些。

Congress will stiffen oversight of offshore drilling and boost the penalties for lapses .

国会将严格监管近海石油开采并加大对出现差错的惩罚力度。

Joints stiffen as their molecular mesh of collagen tightens , the same process that helped to strengthen them in early life .

关节的胶原蛋白分子网格收紧造成了关节僵硬；同一过程在生命初期有助于强化关节。

Flammang thinks the shark uses the muscle she characterized to stiffen the tail midswing , changing its shape slightly , to throw off the extra vortex .

弗拉芒认为鲨鱼使用她之前描述的那块肌肉让尾巴在摆动中变硬，并轻微地改变形状来摆脱额外的漩涡。

Over the years , the heart and artery walls thicken and stiffen , which often results in high blood pressure and plaque buildup .

随着年龄增长，心脏和动脉壁增厚，僵硬，这往往导致血压升高和血小板积聚。