Suspense account

Hi sir, I’m totally confused between these two questions.

1.
The trial balance of Kelvin does not balance.

Which TWO of the following errors could explain this, assuming that Kelvin maintains
control accounts for its receivables and payables within the double entry system?

(1)
The sales day book was undercast by $100.

(2)
Discounts received were credited to sales revenue account.

(3)
An opening accrual was omitted from the rent account.

(4)
The debit side of the cash account was undercast.

A (1) and (2)
B (2) and (3)
C (3) and (4)
D (1) and (4)

2.
In an accounting system where individual receivables and payables
ledger accounts are maintained as an integral part of the double
entry system, which of the following errors will not be identified by a
trial balance?

A overcasting of the sales day book

B undercasting of the analysed cash book

C failure to transfer a non-current asset to the disposal account when
sold

D transposition error in an individual receivables account

In the first question the ans is 3&4, the second questions ans is C.

My doubt is that,
in the first question, why there is no suspense a/c for- sales day book was undercast by 100. While in the second question there’s a suspense a/c for-
A. Overcasting sales day book.

Is it because, he maintains control accounts for receivables and payables in the first question but individual payable and receivable ledger in the second question?

Please help. Thanks.