よりほかない・ざるを得ない・しかない: the difference
よりほかないN2
Meaning
To have no choice but, No other way than, Have to
Past papers
Example
ゴルフの解説者：「このコースレイアウトだと、刻むよりほかないですね。」
Golf commentator: 'If it is this course layout, there is no choice but to lay up the ball.'
ざるを得ないN2
Meaning
Can't help doing, Have no choice but
Past papers
Tested 3 times in past papers
Example
サプライズのプレゼントに、驚かざるを得なかった。
I couldn't help but be surprised at the surprise present.
しかないN3
Meaning
Have no choice but to, Can only
Past papers
Tested 3 times in past papers
Example
人が多いから、並ぶしかない。
Because there are a lot of people, we have no choice but to line up.
How to tell them apart
「よりほかない」: all other options are used up, only one is left; formal.
「ざるを得ない」: very unwilling, but forced by the situation.
「しかない」: the most common in speech, light and direct.