Which of the following birth control measures can be considered as the safest?

Natural methods of contraception work on the principle of avoiding chances of ovum and sperm meeting. It includes

$A.$ Periodic abstinence

$B.$ Withdrawal

$C.$ Coitus interruptus

$D.$ Lactational amenorrhoea

Oral contraceptive pills contain

Progestogens alone or in combination with estrogens can be used as a contraceptive in the form of

Assertion : Copper $-T$ is an effective contraceptive device in human females.

Reason : Copper $-T$ prevents passage of sperms from vagina upwards into fallopian tubes.