想必是

闻其声 想必是 位女子

(竟遇见了他) ── Previous context

“Judging by the voice, you must be a lady.”

想必是 圣上的孝心所致吧

(那莫非圣上 是故意输给太后和大长公主的) ── Previous context

“It must be due to His Majesty's filial piety.”

想必是 定王的新妇吧

(这位) ── Previous context

“You must be Prince Ding's newlywed bride?”

想必是 有他自己的道理

(师父既然不愿意深聊) ── Previous context

“he must have his reasons.”

想必是 手到擒来

(这些小事) ── Previous context

“is nothing for him.”

想必是 从小就擅琴吧 哪里

(这么吵闹的地方 魏副尉还能听音识曲) ── Previous context

“You must've been good at the zither since you were young. Not at all.”

高嫁之人 更是不容易 想必是 为了嫁妆

(崇尚奢婚) ── Previous context

“It's even more difficult for a woman marrying into a higher status. They're probably strapped for cash”

想必是 有什么要紧的事

(公孙先生特意赶来) ── Previous context

“it must be for something important.”