Question

you had better .....
.....to him at once to tackle the problem.
(a) talked (b) talk (c) taking
(d) to talk​

Answer 1

Here is the answer:

You had better talk to him at once to tackle the problem.

Explanation

‘had better/best’(do something) is an idiomatic expression that is used to tell someone what they should do.

Example

We had better hurry to the station now or we’ll miss the train.  

Answer 2

(B) talk is the correct answer ✔️